Arxiu d'etiquetes: climate change

The humans have done it again: the Anthropocene, another shameful achievement for mankind

Science books have to be modified again. Joining other famous geological epochs of the Cambrian, Jurassic or Pleistocene another one must be added from now: the Anthropocene. On August 2016 a group of experts confirmed what everyone suspected: mankind have been so interventionist in terrestrial processes that the natural cycle have changed irretrievably. We have already suffering the consequences, and the human footprint on our planet will be present until after our demise

INTRODUCTION

The history of the modern man, Homo sapiens sapiens, was not easy in the beginning. It is believed that we appeared on the Middle Paleolithic, about 200,000 years ago in Africa. In those days humans were already good hunters, but also good preys, and although the species was thriving and spreading across the planet, this was done slowly and always influenced by severe climate changes. It took 100,000 years to leave Africa and anothers 80,000 to reach America. During all that time and until almost the present day, humans being was at the mercy of the Earth and its whims, which decided at will the fate of our ancestors. However, the Ice Age ended, the Holocene began and thereby unprecedented technological advancement. The industrial revolution definitely transformed humans and the way they interact with the world, which suffered the devastating consequences of an ambitious and unaware species about their enormous global influence.

mamut
Humans have been nomadic most of their existence, with a strong dependence on environmental conditions that conditioned their prey. With the agriculture and lifestock the first villages were created, leading to the modern style. Source: Return of Kings.

WHAT IS A GEOLOGICAL TIME AND HOW IT IS POSSIBLE TO ENTER AND LEAVE IT?

At first glance, it may seem a mere syntactical question or a whim of geologists. However, designate a geological time is important when defining long periods of time sharing similar environmental conditions. Normally, a geological period usually lasts no less than 2 million years, and the fossil record is used to find out a major discontinuity in the typical pattern of the biota of that actual period. Therefore, an epoch tend to finish when an abrupt climate change occur (the Pleistocene ends with the last of the great glaciations), leading to changes in the biota (the meteorite that wiped out the non-avian dinosaurs caused the end of the Cretaceous period). However, these abrupt changes must be occur globally and in a short space of time to really be considered as a different geological epoch.

geological-time-scale
Earth is divided into periods whichare divided into geological epochs. These periods are marked by relatively stable and / or with a characteristic biota. These epochs are usually finished by events that involve drastic changes for living organisms on a global scale. Source: philipmarshall.net.

THE ANTHROPOCENE

The term is not new (it was used for the first time in the mid XIX century during the industrial revolution) but regained importance in early 2000, thanks to Paul Crutzen. This chemist, together with other colleagues, discovered the compounds that were destroying the ozone layer, which makes him to win the Nobel Prize in Chemistry. In his speech, he had special interest in stressing that the Holocene “was over forever” to make way for the Anthropocene, the age of humans. His article in Nature about the Anthropocene was a reference for many scientists working on projects about environmental problems in the Anthropocene epoche. On August 29, 2016, the expert group of the Anthropocene voted at the International Geological Congress (IGC) to formally establish the Anthropocene as a new geological epoch.

Grinding Shop
The industrial revolution changed the course of Earth forever. Vast amounts of fossil fuels were burned and their products emitted into the atmosphere. The production system took a turn, giving priority to production and thereby to make unprecedented use of the planet’s resources. In the photo, British workers in a factory of agricultural products in 1928. Source: Daily mail.

BUT, WHY ARE WE IN THE ANTHROPOCENE?

As we mentioned before, to change the geological epoch it has to be evident that environmental conditions are changing on a global scale. And that is what is happening since the early 50s of the last century, date in which researchers have officially marked the beginning of the Anthropocene. In this Science article, researchers from around the world gathered geological evidence showing with certainty that mankind has changed the planet severely and it should already talk about another geological era. The researchers also pointed to the products of the many atomic tests of the 50s as the starting point of the Anthropocene.

mushroom-cloud-of-first-hydrogen-bomb-test
The nuclear tests of the 50s, like this one in which the first hydrogen bomb (Ivy Mike) was tested, caused the release of large amounts of radioactive materials into the atmosphere. These particles were settled and that has allowed researchers to have evidence in order to demonstrate the impact of human actions on a global scale. Source: CBC.

EVIDENCE OF THE ANTHROPOCENE

Since the beginning of the industrial revolution, more than two centuries ago, numerous anthropogenic deposits have been accumulated in the earth’s crust, from new minerals and rocks to aluminum, cement and petroleum products such as plastics. Just after these lines, we show the main evidence put forward by researchers to justify the change of epoch:

High levels of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), plastics, fertilizers and pesticides in sediments. The burning of oil, coal and other wood products are the source of large amounts of PAHs in the atmosphere, that they just finally end settling in the earth’s crust and living things.Referring to fertilizers, little abundant nutrients in the soil such as nitrogen and phosphorous have doubled in the last century due to the increasing number of crops, many of which following the intensive model to maximize production. Moreover, plastics are already present worldwide. Its high resistance to degradation prevents natural recycling, which causes large quantities to deposit and, especially, to end in the sea, where there are authentic plastic islands, as the Great Pacific garbage patch .

plastics
Plastic is the most widely-product made from oil on Earth. Its impact on the environment is one of the most serious at present, and  global sedimentation leaves traces of our presence until thousands of years after our disappearance. Source: The Guardian.

Radioactive elements of nuclear tests. The detonation of the atomic bomb called Trinity in 1945 in New Mexico (USA), was followed by a long list of other nuclear tests during the Cold War. As a result, large amounts of carbon-14 and plutonium-239, among other molecules, were released into the atmosphere and sedimented years later in many parts of the globe, constituting a proof of the great human impact on Earth.

sediment
This core, extracted by the geologists that have determined that we are in a new era, shows the accumulation of human origin material in the sediments of a lake in Greenland. In it was found pesticides, radioactive nitrogen, heavy metals, increases in the concentration of greenhouse gases and plastics. Source: Science.

High concentrations of CO2 and CH4 in the atmosphere. From 1850 and especially in the following decades, the levels of these gases in the atmosphere broke with the typical pattern of the Holocene, getting itself to achieve, in our century, 400 ppm (parts per million) of CO2, an increase of more of 150 points from the pre-industrial situation. This increase in atmospheric CO2 has a direct impact on the temperature of the Earth. It is believed that the global temperature has increased by around 1 ° C since 1900, and will increase between 1.5 and 3.5 ° C by the year 2100.

aumento-co2
This chart shows the unprecedented increase in CO2, methane and nitrous oxide in the atmosphere. Although CO2 is the best known gas and which has the greatest impact on a large scale, the other two gases have greater power to limit heat dissipation into space. The increase of these gases is closely related to the increase of global temperature. Source: CSIRO.

The increase of the ratio of extinction of living organisms in all parts of the world as a result of human activities. Since 1500 the extinction of species by humans has increased, but is from the XIX century onwards when the extinctions are present in the entire planet. The distribution of species has been disrupted due to human activities such as agriculture and deforestation and the introduction of invasive species, causing changes in the habits of native species and often come to displace and even to extinguish. This unprecedented high extinction ratio is considered by many people as an unmistakable symbol that we are in front of the sixth mass extinction on Earth.

ratio-extincion
Since the beginning of the industrial revolution, the rate of extinction of vertebrates is 100 times greater than in the past. At this rate, it is estimated that in the following centuries the number of extinct species will reach 75% of the existing ones. The dotted black line in this graph shows the rate of pre-industrialization extinction, while others refer to the cumulative percentage of extinct species since 1500. Source: Science.

FUTURE

Whatever the fate of humanity and future actions undertaken to mitigate climate change, what is clear is that the human footprint will remain indelible in the earth’s surface for millions of years, similar to what occurred after the Permian or Cretaceous mass extincion. The strata will show the follies and excesses carried out by us, perhaps as a warning for the following species that dares to relieve humanity of its status as the dominant species.

REFERENCES

Ricard-anglès

 

The Arctic: who cares?

The global change is the main threat to the Arctic, due to the increasing temperature is melting their ice coverage. What will be the consequences of this for its fragile ecosystem? Who cares about it?

THE ARCTIC AND ITS IMPORTANCE

The Arctic, one of the few unspoiled areas of the planet, is located in the north pole. Low temperatures in the region (an average of -35°C in winter and 0ºC in summer) are explained by the low insolation due to the inclination of the globe.

Before the industrial age, the permanent ice of the Arctic occupied about 7 million square kilometers (doubling its size in winter), but it is increasingly difficult to maintain that ice in summer. The ice may reach a thickness of 50 meters in winter, dropping to 2 meters in summer.

Before you start, you can enjoy this video with stunning images of the Arctic:

LIFE IN THE ARCTIC

The Arctic offers a wide variety of different environments: ocean, ice sheets, the coastal area, the tundra and some coniferous forests.

importancia ártico
The tundra is most notable terrestrial biome in the Arctic (Picture: Biomas).

This allows the livelihood of many plant and animal species. Only in the Arctic Ocean, it has been described more than 5,000 animal species, some of which are endemic to this area. An estimated 400 species live only in the Arctic region.

Among the best known animals, we find the bowhead whale (Balaenoa mysticetus), a large animal that can live more than 100 years, and the narwhal (Monodon monoceros), cetacean in which males have a very long tusk, used during courtship.

importancia ártico ballena groenlandia
Bowhead whale (Balaena mysticetus) is an endemic animal of the Arctic (Picture: Clarín).

On ice and snow, polar bear (Ursus maritimus), walrus (Odobenus rosmarus), the Arctic wolf (Canis lupus arctos) and the reindeer (Rangifer tarandus) are present.

lobo ártico
Arctic wolf (Canis lupus arctos) is endangered (Picture: Deanimalia).

The Arctic is also home to over 80 species of birds, including the Brünnich’s guillemoth or the king eider; and more than 400 fish.

But undoubtedly, the group that takes the cake are arthropods, with more than 1,500 documented species, although there are also representatives of almost all existing animal phyla.

Este copépodo, de la especie Euaugaptilus hyperboreus, forma parte el zoopláncton ártico (Foto: Poetic Monkey).
This copepod (Euaugaptilus hyperboreus) is part of Arctic zooplankton  (Picture: Poetic Monkey).

THE ARCTIC IS ESSENTIAL TO CLIMATE

The Arctic, along with Antarctica, is like a natural air conditioner on the planet. Therefore, malfunction further enhances the effects of climate change.

The ice cover is responsible for a high percentage of albedo. Albedo is the effect by which a surface reflects part of the solar radiation back into the atmosphere, thus maintaining a lower temperature. Without this effect, the temperatures will be increasingly high.

El hielo es el principal elemento del albedo en la superficie de la Tierra (Foto: US Satellite).
Ice is the key element of albedo in Earth surface (Picture: US Satellite).

The physical processes taking place in the Arctic affect ocean circulation worldwide: during the formation of sea ice, water crystals exclude salt, so that water is increasingly salty. The increase of salinity, along with the low water temperatures, cause the formation of a very dense water mass that sinks to the ocean floor and is transported southward through the thermohaline circulation, responsible for regulating the global climate. Without ice, the thermohaline circulation may be interrupted or weakened, with the consequences that would follow.

La circulación termohalina es responsable del clima a nivel mundial (Foto: Blog de recursos de Cpmc).
The thermohaline circulation is responsible of worldwide climate (Picture: Blog de recursos de Cpmc).

ARCTIC AND CLIMATE CHANGE

Due to the increase in temperature on a global level, the ice covering the Arctic has been reducing. Several reports indicate that this reduction was  about 30% in just two decades. Also, if this trend continues, in twenty years might disappear all Arctic ice, at least during summer. Without ice, many species will have serious problems to survive, such as the polar bear, seals and other pinnipeds.

hielo ártico permanente
(Picture: India Today).

As we have seen, no ice, no albedo; but also if the permanent ice melts, it will cause the release of large amounts of greenhouse gases that are trapped in either the ice or in the frozen Arctic soil (permafrost); providing a positive feedback to climate change.

Some studies suggest that, if the entire Greenland ice melt the average sea level will rise 7 meters.

In addition, increasingly massive algal blooms occur, which sink and cause eutrophication of the ecosystem. The ice thickness reduction allows increasing carbon dioxide in water to penetrate, causing water acidification, which can cause bleaching of coral and shells malformations in animals.

There are many companies that see the melting of the Arctic as a commercial possibility:

  • Obtaining energy resources such as natural gas and oil (for only 3 years, according to experts).
  • Exploitation of mineral resources such as manganese, gold, lead and diamonds.
  • New fishing grounds.
  • New trade routes for shipping and tourism.

Thus, the Arctic is a very fragile ecosystem that we must protect together. Acting locally, we are acting globally.

REFERENCES

  • Broecker, WS (2005). The role of the ocean in climate: Yesterday, today and tomorrow. Eldigio Press
  • El mar a fondo: El agua de mar y las corrientes oceánicas (Guía didáctica).
  • McIntyre, A (2010). Life in the World’s Oceans. Blackwell Publishing Ltd.
  • Greenpeace (2013). El Ártico y los efectos del cambio climático en España. Salvar el Ártico es salvar mucho más. Greenpeace.
  • Hutchinson, S & Hawkins, LE (2004). Océanos. Libros Cúpula. Coleccion Biblioteca visual
  • Palacín, B (2010). La creciente importancia el Ártico. Revista Española de Defensa
  • Perrin, WF; Würsig, B & Thewissen, JGM (2009). Encyclopedia of Marine Mammals. Academic Press (2 ed)
  • Cover picture: Kerstin Langenberger

Difusió-anglès

Disease outbreaks, another effect of climate change?

We know that many infectious diseases depend on climatic factors such as temperature. So, can climate change cause an increase of the outbreaks? Let’s find out!

HEALTH AND CLIMATE CHANGE

 According to some surveys conducted by the Pew Research center, 54% of respondents believe that climate change is a serious problem and their major concerns include drought, intense rainfall and heat. If you are interested in to learn more about this survey, you can find them in the following article.

These changes have a negative effect on human health. The World Health Organization (WHO) expected that between 2030 and 2050 climate change will cause some 250,000 additional deaths a year. The effects can be very varied: deaths by  heat, floods, increase in respiratory diseases, stress etc. One of the important health effects is an increase in the transmission of infectious diseases.

climate_change_health_impacts600w
Graphic of impacts of climate change on human health (Photo: CDC)

Infectious diseases are closely related to  environment’s characteristics (such as temperature and humidity). In some cases, these diseases are transmitted by vectors (bats, arthropods, snails, rodents, ticks…). A  temperaturerising  will modified its geographical distribution, seasonality and population size. An example is  the presence of the mosquito Aedes albopictus, known as mosquito tigre, in Spain.

On the other hand, changes in the use of the soil, overcrowding of cities, poor hygienic habits and other socio-economic factors also have an effect in the transmission of certain diseases. For example, deforestation and poor hygiene of the population increases the breeding sites of the mosquitoes, causing an increase in the probability of malaria transmission.

tabla_cambioshumanos_
Human activities may effect diseases transmission rate. (Photo: OMS)

VECTOR DISEASES

Vector diseases are those that are transmitted through a vector animal (whether a mosquito, rodent, tick, snail, bat…). These diseases may be zoonotic (animal to human, as rabies) or antroponotic (among humans, such as malaria or dengue). If you want to know more about the effects of climate change on vector, feel free to access this article.

Sin título
Different types of vector diseases. (Photo: OMS)

There are many vector diseases which should be monitored in the coming years, as for example the malaria, dengue fever chikungunya, Boutonneuse etc. Let’s look at the two best known infectious diseases.

MALARIA

This disease is caused by parasites of the genus Plasmodium, which is transmitted by the bite of mosquitoes of the genus Anopheles. There are four different types of malaria, but the most deadly is that caused by the species Plasmodium falciparum.

p_falci_cdc
Plasmodium falciparum gametocyte. (Photo: CDC)

The WHO estimates that in the year 2013, 198 million people were infected,  584,000 of which died. It is expected that these numbers will increase due to climate change. Temperature rise leads to an increase in the infective period of the mosquito and the modification of vector’s geographical distribution. Possibly in the next few years, if the trend does not change, there will be an increase in the spread of the disease in endemic areas  and will probably resurface in other areas (red areas on the map).

global_warming_climate_change__malaria
Estimation of the spread of malaria in 2050 (Photo: Randolph Rogers)

In Spain, the autochthonous malaria was eradicated in 1964. Currently, the spanish cases of malaria are imported from countries with indigenous malaria. Even so, note the geographic situation of our country, the rising temperatures, the presence of a competent vector and the presence of imported parasit, significantly increase the likelihood of disease’s transmission.

DENGUE FEVER

This is a viral disease (caused by viruses of the genus Flavivirus) that is transmitted by the bite of mosquitoes of the Aedes genus (including the Tiger mosquito). Dengue fever is a widespread disease in tropical countries, although its suffering geographical changes due to changes in temperature, precipitation and a demographic overcrowding of the cities.

dengue
Structure of dengue fever virus (Photo: César Cabezas)

Before 1970, only nine countries had experienced serious dengue epidemic episodes. In recent decades, the cases have increased sharply. According to WHO estimates, each yerar are produced about 390 million infections,  23%  of which are clinically manifested.

12889_2014_6968_Fig3_HTML
forecast of the spread of dengue fever in Europe during the twenty-first century. Expressed in nº of cases /100.000 habitants. (Photo: Moha Bouzid)

As in the case of malaria, current climatic variations alter the geographical distribution of the vector. As we can see in the previous map, the predictions for this century, if conditions do not change, are a significant dengue fever cases increase in Northern Europe (lighter areas are potential sites of infection). As we see in the case of Spain, the Mediterranean would be the region that would have more cases of dengue fever.

WATERBORNE DISEASES

Climate change also affects the water cycle. The news about weather disasters (floods, strong drought, torrential rains, hurricanes…) never cease to appear in the media. These climatic variations affect those diseases that are spread by water, either by contamination of the flows, by human migration and low hygiene that exist in certain places of overcrowded cities.

The most known diseases associated with floods and droughts are infections of Cryptosporidium or cholera. Let’s look at this last example.

CHOLERA

Vibrio cholerae is a bacilar bacteria that causes this disease. It is a diarrheal infection that suffer every year between 1.4 and 4.3 million people, 142,000 which end up dying. The transmission of this Bacillus is closely linked to environmental mismanagement. Heavy rains or flooding can cause water pollution, and extreme drought increases the bacterial charge of the existing flows.

vibrio colerae
Microphoto of Vibrio cholerae (Photo: Louisa Howard).

During the 19th century, cholera spread across the world from Ganges (India). The last cholera epidemic began, as we can see in the map, in the South of Asia in 1961. Now cholera has been distributed worldwide due above all to human migrations (bacillus carriers), the agglomeration of people in suburban areas without hygiene habits and climate disasters. The WHO estimates that by 2030 there will be 10% more cases due to climate change.

0291-choleraspread-EN
evolution of last epidemic of cholera (1961-2004). (Photo: IPCC)

It may not be possible to quantify in that measure climate change can affect the transmission of these diseases, since these depend on many other factors (demographic dynamics, immunization, etc.). Is worth mentioning, that the provisions set out in this article are assumptions obtained from current data. That means, that if the mechanisms for the reduction of global climate change works and environmental conditions improve, these data would no longer have any statistical value

·

Remember that it is better to be safe than sorry!

Cares for the environment: the Earth is your home. 

REFERENCES

Maribel-anglès

54% of world population considers climate change a very serious problem

Climate change (or global change if we consider that it doesn’t affect only climate) is a very recurrent topic these days. The reason is that on November 30 started the COP21 in Paris, in which more than 190 nations have gathered, and will finish on December 11. Here, instead of talking about the climate evolution or its possible effects, we are going to talk about the results of a survey made by the Pew Research Center about the world population’s opinion on global change. 

ABOUT THE SURVEY

The survey was carried out from March 25 to May 27, 2015, at 45,435 people from 40 countries around the world.

GENERAL CONCERN

The majority of the people surveyed in all 40 nations consider that climate change is a serious problem. In concrete, 54% consider it a very serious problem. Latin America (mainly Brasil, Chile and Peru) and Africa (principally Burkina Faso, Uganda and Ghana) are even more worried than the global average. However, 85% say global change is a serious problem to some extend.

Moreover, 51% hold that this worldwide issue is harming people now (being Latin America, Europe and Africa more concerned than the global median) and another 40% are very worried that climate change will harm them personally in the future (specially in Latin America). 

Harm personally
Percentage of people very concerned that global climate change will harm them personally (Picture: Pew Research Center, 2015).

What attracts attention is the fact that USA and China, the two countries in the world that produce more dioxide carbon, are among the least concerned. Generally, people from countries that produce more carbon dioxide per capita are less anxious about the climate change. 

WHICH ARE THE BIGGEST FEARS?

In general, 44% of the respondents consider water shortages the major concern and, in fact, is the biggest fear in all regions, followed by sever weather (such as floods or intense storms, 25%), hot weather (14%) and sea level rise (6%).

drought climate change
Droughts are the biggest concern in all polled nations (Picture: Weather Wiz Kids).

Latin America, Africa and USA are more worried by water shortages than the average, while Asia/Pacific and Europe surpass the average of the concern in severe weather.

Climate change concerns
Regional medians of most concerning effects of global climate change (Picture: Pew Research Center, 2015).

HAVE THE PERCEPTIONS CHANGED OVER TIME?

In general, there have been a very little increase in the perception that climate change is a very serious problem. While in 2010 47% of the respondents considered it a very serious problem, in 2015 they are a 49%.

However, in some countries the perception have changed. In some key economies, such as Turkey (reduction of 37%), China (-23%), South Korea (-20%) or Japan (-13%); the number of people saying that climate change is a very serious problem has reduced. On the other side, in Nigeria (an increase of 18%), France (+10%) and in USA (+8%) the concern is now higher.

WHAT SHOULD BE DONE TO DEAL WITH IT?

In 39 of 40 countries (the exception is Pakistan), people consider that their countries should do something to fight against the problem. In specific, 78% of the polled people support the fact that their country should limit greenhouse gas emissions, specially in Europe (a median of 87%) and Latin America (83%).

But this would not be enough. 67% say that people will have to change their lifestyle (mainly Latin Americans and Europeans), while 22% think that thanks to technology the problem will be solved. Probably, a combination of both will be the solution.

Which countries should do more? 54% find that rich countries should do more than the developing ones because they have produced most of the greenhouse gas emissions, while a 38% consider that developing countries should do just as much because they will produce more in the future.

REFERENCES

Difusió-anglès

Why are sea turtles threatened?

Last week, we saw with detail how is the life of a sea turtle. Did you miss it? So, click here to read it! This week, I am still talking about his amazing animals, but I am focusing on the dangers that are threatening them, both natural or anthropic, and which actions we can do to save them. 

NATURAL THREATS 

Sea turtles are threaten by natural and anthropic dangers. Natural threats include egg loss due to the inundation or erosion of the beach, predation at all life stages, extreme temperatures and disease.

Egg loss

High tides and storms can produce the egg loss for several reasons: the drowning of the eggs, the beach erosion or accretion or nests are washed away. Moreover, there are some animals that feed on sea turtle eggs.

seaturtleeggs
There are several reasons that explain the egg loss (Picture: PaddleAndPath).

Predation on turtles

Despite little turtles usually leave the nest at night, the risk of being eaten by a predator is not zero, since they are part of the diet of raccoons, birds, crabs, sharks and other fishes. Young and adult turtles are also feed by some animals, like sharks and other big fishes, but the impact is not as big as in the first stages. Read the post of the last week if you want to know how many turtles die of old age for each 10.000 eggs. The number will shock you!

Els crancs poden menjar-se les tortugues acabades de sortir de l'ou (Foto: Gnaraloo Turtle Conservation Program, Creative Commons).
Crabs eat the hatching turtles (Picture: Gnaraloo Turtle Conservation Program, Creative Commons).

Hypothermia

Below 8º to 10ºC, turtles become lethargic and buoyant until they float at the surface (this condition is known as cold-stunning). At temperatures below 5º to 6ºC death rate can be important.

Diseases

Parasitic infections are common in sea turtles. Up to 30% of the loggerhead sea turtles in the Atlantic ocean have trematodes that infect their cardiovascular system. These infections, at the same time, reduce their immunological defences and then may be infected by bacteria (like Salmonella or E. coli).  Dinoflagellate blooms are also a threat for them because of the poisonous content produce health problems.

ANTHROPIC THREATS

Four are the main anthropic threats for marine turtles: egg and turtle poaching, destruction of nesting beaches, pollution and fisheries by-catch. Here, we will see some more.

Poaching

Fortunately, poaching is not present all over the world, but it can be specially important in some countries. Turtles are hunted for their meat and cartilage or for their shells (used in jewellery and like a decoration). Egg collection is also present.

Tortugues marines comissades per la policia de les Filipines (Foto: Mongabay).
Sea turtles confiscated by Philippine Police (Picture: Mongabay).

Venta d'ous de tortuga marina (Foto: OceanCare).
Sale of sea turtle eggs (Picture: OceanCare).

Destruction of nesting beaches

The building of infrastructures to protect ocean front property produce that females cannot access to nesting beaches and, moreover, produce their erosion. Beach nourishment to fight against beach erosion also affect them because the new beach buries the nests, offshore dredging kills them, beaches may become too compacted for nesting and steep and sand can have different properties (what may reduce, for example, gas diffusion). Tourism also affect them.

Pollution and garbage

It is not completely known if the pollutants, such as fertilizers and pesticides, have a direct impact on sea turtles, but among indirect effects there are the habitat degradation, considering that excess nutrients increase harmful algal blooms.

Garbage is also a problem. Turtles with plastic in the stomach have been found because they confuse plastic bags with jellyfishes, what block intestines and produce their death. Not only are plastics ingested, but also do they become entangled in debris like nets, fishing line or other plastic items. This produces a growth deformation.

La ingesta de plàstics (Foto: Fethiyetimes).
The ingestion of plastic blocks their intestines and produce death (Picture: Fethiyetimes).

Fishing by-catch

Sea turtles are also threaten by fishing by-catch.

Drift fishing, although is forbidden in Spain, are still used and every year, each boat produce the death of a hundred animals.

The longline fishing has an important impact. In Spanish waters, every year, are captured between 15,000 and 20,000 individuals. Despite they return alive to the ocean, they have a hook in the mouth and produce post release death for the wounds. Here you can read a review of the methods to reduce by-catch on loggerhead sea turtle in longline fishing. 

La pesca de palangre captura entre 15.000 i 20.000 exemplars cada any en aigües espanyoles (Foto: Phys).
Longline fishing captures between 15,000 and 20,000 individuals in Spanish waters each year (Picture: Phys).

Mortality in trawling depends on trawl times: mortality increased from 0% with times less than 50 minutes to 70% after 90 minutes. This is explained by the breathing capacity of the animals.

Global change

Ocean acidification due to the continued release of carbon dioxide may have an important impact on sea turtle populations because the quality of the food will probably reduce.  The sea level rise will have a negative impact on sea turtles because endanger the existence of beaches. Moreover, the increase in the temperatures will affect the growth and the sex ratio, since sex depends on the temperature in reptiles: below 29ºC prevail males and above, females.

HOW CAN WE HELP THEM?

  • Avoid any activity or behaviour that can annoy sea turtles. In the case of feeling annoyed, you will observe that they try to leave the area, they do a fast diving and they do abrupt swimming movements.
  • Reduce the speed of the ship if you see any element that could be a sea turtle. In the case of being a turtle, avoid any manoeuvre that can endanger them.
  • Pick up fishing gear or garbage present in the water.
  • In the case of the animal being in danger, first, call the emergency phone of your country. In the case of Spain, call 112. However, there are some actions that you can do while vets arrive:
    • Turtle with a broken shell or open injuries: cover the injuries with a wet rag with iodine (never in the eyes, ears and nose).
    • Drowned turtle: maintain the animal for 5 minutes with the ventral part face up and with the body inclined (head downwards), moving its fins.
    • Turtle with plastics in the mouth: remove the plastic taking care and call the emergency number.
    • Dead turtle: don’t touch the animal and call emergencies.
    • Hooked turtle: don’t stretch the hook and cut the line with 30 cm.
  • Inform the proper authority of the location of possible nests. Some clues:
    • Tracks of turtles in the sand of the beach, with a shape of a V, with the nest in the vertex.
    • Depression in the sand, what indicates about the eclosion of eggs.
    • Observation of a turtle doing the lay.
    • Remainder of eggs or hatching animals.

REFERENCES 

  • Consejería de Medio Ambiente de la Junta de Andalucía (2014). Varamientos de Especies Marinas Amenazadas. Guías prácticas voluntariado ambiental.
  • Gray, J (1997). Marine biodiversity: patterns, threats and conservation needs. Biodiversity and Conservation 6, 153-175
  • Hamann, M et al. ‘Climate Change And Marine Turtles’. The Biology Of Sea Turtles. Volume III. Jeanette Wyneken, Kenneth J. Lohmann and John A. Musick. 1st ed. New York: CRC Press, 2013. 353-378. Print.
  • Harrould-Kolieb, E. & Savitz, J. (2009). Acidificación: ¿Cómo afecta el CO2 a los océanos? Oceana
  • Ministerio de Agricultura, Alimentación y Medio Ambiente. Guía de buenas prácticas en las Zonas Especiales de Conservación de ámbito marino de Canarias. España. http://www.magrama.gob.es/es/costas/temas/proteccion-medio-marino/201311_guia_bbpp_web_tcm7-229984.pdf
  • Oceana (2006). Las tortugas marinas en el Mediterráneo. Amenazas y soluciones para la supervivencia. 38 pp.
  • Otero, M., Garrabou, J., Vargas, M. 2013. Mediterranean Marine Protected Areas and climate change: A guide to regional monitoring and adaptation opportunities. Malaga, Spain: IUCN. 52 pages.
  • Shigenaka, G (2010). Oil and Sea Turtles. Biology, planning and response. NOAA
  • Smith, T & Smith R (2007). Ecología. Pearson Educación (6 ed.)
  • Velegrakis, A., Hasiotis, T., Monioudi, I., Manoutsoglou, E., Psarros, F., Andreadis, O. and Tziourrou, P., (2013). Evaluation of climate change impacts on the sea-turtle nesting beaches of the National Marine Park of Zakynthos Protected Area. Med-PAN North Project, Final report, 81 pp.

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How do temperature and global warming affect the sex of reptiles?

In most animals the sex of an individual is determined at the moment of fertilization; when the egg and the sperm fuse together it is fixed if that animal will be male or female. Yet in many reptilian groups sex determination is established later during incubation, and the determinant external factor is the incubation temperature of the eggs. In reptiles, this means that the environment plays a crucial role in determining the sex ratio emerging from an egg clutch, and that these animals are very susceptible to alterations in temperature caused, for example, by climate change.

SEXUAL DETERMINATION: GSD VS TSD

In the majority of animal species, sexual differentiation (the development of ovaries or testes) is determined genetically (GSD). In these cases, the sex of an individual is determined by a specific chromosome, gene or allele which will cause the differentiation to one sex or the other. In vertebrates there exists two main types of GSD, the XX/XY system in mammals (in which XX is a female and XY is a male) and the ZW/ZZ system in birds and some fishes (ZW corresponds to a female and ZZ to a male).

Types_of_sex_determinationExamples of different types of genetic sexual determination systems found in vertebrates and invertebrates, by CFCF.

In the case of reptiles, there is a great variety of sexual determination mechanisms. Some present GSD models; many snakes follow the ZW/ZZ system and some lizards the XX/XY. Still, in many groups the sex of the offspring is determined mainly by the egg incubation temperature (TSD), and therefore the environment plays an important role in the proportion of males and females found in a population.

Eastern_Bearded_Dragon_defenceThe eastern bearded dragon (Pogona barbata) is an example of a reptile with GSD, but which is also affected by incubation temperature. Photo by Trent Townsend.

Nevertheless, the genetic and temperature sexual determination are not mutually exclusive. Reptiles with TSD have a genetic base for the ovarian and testicular differentiation which is regulated by temperature. Similarly, it’s been observed that in reptiles with DSG, such as the eastern bearded dragon (Pogona barbata), high temperatures during incubation causes genetically male individuals (ZZ chromosomes) to develop functionally as females. This proves that in reptiles, there is no strict division between GSD and TSD.

TEMPERATURE AND SEX

The incubation period during which the sex of an individual is determined is called thermosensitive period and usually corresponds to the second third of the incubation period, during which temperature must be maintained constant. This critical incubation period usually lasts between 7 and 15 days, depending on the species. After this period the sex of an individual usually cannot be reversed (all or nothing mechanism).

Audobon Zoo, New Orleans, LouisianaKomodo dragon baby (Varanus komodoensis) hatching. Photo by Frank Peters.

Temperature during the critical incubation period affects the functioning of the aromatase, a hormone which converts androgens (masculinizing hormones) to estrogens (feminizing hormones). At male-producing temperatures, the activity of the aromatase is inhibited, while at female-producing temperatures the activity of the aromatase is maintained.

AromatassssssaGraphics of the aromatase’s activity related to gonadal hormones on European pond turtle’s embryos (Emys orbicularis) at 25oC (males) and at 30oC (females), during the critical incubation period, from Pieau et al. 1999.

The TSD is found in all reptile groups except snakes (which have the ZW/ZZ system). In lizards and turtles we can find both genetic-based and temperature-based sexual determination, while in tuataras and crocodilians sex is determined exclusively by temperature. Currently, different patterns of temperature sex determination are known.

PATTERN I

This pattern is the simplest one, in which higher incubation temperatures produce one sex and lower incubation temperatures produce the other sex. Intermediate temperatures usually produce individuals of both sexes and very rarely, intersex individuals. This pattern can be further divided in:

  • Pattern Ia TSD, in which eggs incubated at warmer temperatures produce high female percentages and eggs incubated at cooler temperatures produce high male percentages. This pattern is found in many species of turtles.
Emys_orbicularis_portraitPhoto of a European pond turtle (Emys orbicularis), species that follows the pattern Ia TSD; at 25oC or less during incubation only males are born, while at 30oC or more only females are born. Photo by Francesco Canu.
  • Pattern Ib TSD, in which the contrary occurs; high temperatures produce males and low temperatures produce females. We find this pattern in some lizards with TSD and in the tuataras.
TuataraThe tuatara (Sphenodon punctatus) is one of the reptiles that follows the pattern Ib TSD; the pivotal temperature is between 21-22oC, above which males will be born and below which females will be born.

PATTERN II

This pattern is a bit more complex than the previous one. In this one, embryos incubated at extreme temperatures (very high or very low) will differentiate to one sex, while the ones incubated at intermediate temperatures will differentiate to the other sex.

CrocnestPhoto of different aged American alligators (Alligator mississippiensis). These reptiles follow the pattern II TSD; at about 34oC males are born, and at higher and lower temperatures, females are born.

This pattern appears in crocodilians, some turtles and in many lizards. Recent phylogenetic studies indicate that this is the ancestral TSD model in reptiles. Some people even argue that all the TSD cases belong to the pattern II, but that in nature temperatures never reach both extremes, although this is yet to be proved.

TEMPERATURE DETERMINED SEX: PROS AND CONS

Even today the evolutionary advantages of the sex determination by temperature are not fully understood. The case of the reptiles is pretty curious because birds, mammals and amphibians determine their sex genetically in most cases, while in reptiles there is a bit of everything.

Currently, there are studies which are being conducted to see if certain temperatures improve the health of males and if other temperatures the health of females. In one of these studies, it was observed that snapping turtles incubated at intermediate temperatures (which produced both males and females) were more active than the ones incubated at temperatures producing only one sex, making them more vulnerable to be attacked by sight-based predators. Currently, there isn’t enough evidence that indicates to what extent these discoveries could be applied. It is possible that reptiles with TSD are able to manipulate the sex of its offspring, altering the proportion of sexual hormones based on the temperature of their nesting site.

Snapping_turtle_eggs_mdCommon snapping turtle (Chelydra serpentina) an American fresh-water chelonian, laying its eggs. Photo by Moondigger.

The disadvantages of the TSD are much easier to predict.  Any change in the environmental temperature of the nesting areas may affect negatively the populations of a determined species. If a previously shadowy forest is cut down or buildings are constructed in a previously sunny place, the microclimates of the egg clutches of any reptile nesting there will be changed.

Global change, or climate change, represents an additional threat to reptilians with TSD. The rise of the average temperature on the planet and the temperature fluctuation from one year to another, affect the number of males and females that are born in some species of reptiles. This phenomenon has been observed, for example, in painted turtles (Chrysemys picta), in which it has been predicted that a rise of 4oC in their habitat’s temperature could cause the extinction of the species, because only females would be born.

baby-painted-turtle-chrysemys-pictaBaby of a painted turtle (Chrysemys picta), species in which incubation temperatures between 23-27oC produce males, and temperatures above and below it produce females (pattern II). Foto de Cava Zachary.

REFERENCES

During the elaboration of this entry the following sources have been used:

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The plants and the climate change

Since a few years ago, we have heard about the climate change. Nowadays, it is already evident and also a concern. This not only affects to us, the humans, but to all kind of life. It has been talked enough about the global warming, but perhaps, what happens to the vegetation has not been much diffused. There are many things affected by climate change and vegetation is also one of them. In addition, the changes in this also affect us. But, what are these changes? how can the vegetation regulate them? And how we can help to mitigate them through plants?

CHANGES ON PLANTS

Biomes distribution

In general, due to climate change, an increase of precipitations in some parts of the world are expected, while in others a decrease is awaited. A global temperature increment is also denoted. This leads to an alteration in the location of the biomes, large units of vegetation (e.g.: savannas, tropical forests, tundras, etc.).

biomes
Biome triangle classified by latitude, altitude and humidity (Author: Peter Halasaz).

On the other hand, there is an upward trend in the distribution of species in the high latitudes and a detriment in the lower latitudes. This has serious associated problems; the change in the species distribution affects their conservation and genetic diversity. Consequently, the marginal populations in lower latitudes, which have been considered very important for the long-term conservation of genetic diversity and due their evolutionary potential, are threatened by this diversity loss. And conversely, the populations in high latitudes would be affected by the arrival of other competing species that could displace those already present, being as invasive.

Species distribution

Within the scenario of climate change, species have some ability to adjust their distribution and to adapt to this.

But, what type of species may be responding more quickly to this change? It appears that those with a faster life cycle and a higher dispersion capacity will be showing more adaptability and a better response. This could lead to a loss of some plants with slower rates.

Galactites tomentosa
The Purple milk Thistle (Galactites tomentosa) is a plant with a fast life cycle and high distribution capacity  (Author: Ghislain118).

One factor that facilitates adjustment in the distribution is the presence of wildlife corridors: these are parts of the geographical area that enable connectivity and movement of species from one population to another. They are important because they prevent that some species can remain isolated and because they can also allow the movement to new regions.

Another factor is the altitudinal gradient, which provides shelter for many species, facilitates the presence of wildlife corridors and permits redistribution of species along altitude. Therefore, in those territories where there is greater altitudinal range, the conservation is favored.

In short, the ability of species to cope with climate change depends on the plant characteristics and the territory attributes. And, conversely, the species vulnerability to climate change occurs when the speed to displace their distribution or adapt their lives is less than the climate change velocity.

At internal level

Climate change also affects the plant as an organism, as it causes changes in their metabolism and phenology (periodic or seasonal rhythms of the plant).

One of the effects that pushes the climate change is the carbon dioxide (CO2) concentration increase in the atmosphere. This could produce a fertilization phenomenon of vegetation. Due the COincrease in the atmosphere it also increases the uptake by plants, thus increasing the photosynthesis and allowing greater assimilation. But, this is not all advantages, because for this an important water loss occurs due that the stomata (structures that allow gas exchange and transpiration) remain open long time to incorporate CO2. So, there are opposing effects and fertilization will depend on the plant itself, but the local climate will also determine this process. Many studies have shown that various plants react differently to the COincrease, since the compound affects various physiological processes and therefore there are not unique responses. Then, we find a factor that alters the plant metabolism and we cannot predict what will be the effects. Furthermore, this fertilizer effect is limited by the nutrients amount and without them production slows.

fotosíntesi
Photosynthesis process (Author: At09kg).

On the other hand, we must not forget that climate change also alters the weather and that this affects the vegetation growth and its phenology. This can have even an impact on a global scale; for example, could produce an imbalance in the production of cultivated plants for food.

PLANTS AS CLIMATE REGULATORS

Although one cannot speak of plants as regulators of global climate, it is clear that there is a relationship between climate and vegetation. However, this relationship is somewhat complicated because the vegetation has both effects of cooling and heating the weather.

The vegetation decreases the albedo; dark colours absorb more solar radiation and, in consequence, less sunlight is reflected outward. And besides, as the plants surface is usually rough, the absorption is increased. Consequently, if there is more vegetation, local temperature (transmitted heat) intensifies.

But, on the other hand, by increasing vegetation there is more evapotranspiration (set of water evaporation from a surface and transpiration through the plant). So, the heat is spent on passing the liquid water to gas, leading to a cooling effect. In addition, evapotranspiration also helps increase local rainfall.

Biophysical effects of landcover
Biophysical effects of different land uses and its consequences on the local climate. (From Jackson et al. 2008. Environmental Research Letters.3: article 0440066).

Therefore, it is an ambiguous process and in certain environments the cooling effect outweighs, while in others the heating effect has more relevance.

MITIGATION

Nowadays, there are several proposals to reduce climate change, but, in which way can the plants cooperate?

Plant communities can act as a sinks, carbon reservoirs, because through CO2 assimilation, they help to offset carbon emissions. Proper management of agricultural and forest ecosystems can stimulate capture and storage of carbon. On the other hand, if deforestation were reduced and protection of natural habitats and forests increased, emissions would be diminished and this would stimulate the sink effect. Still, there is a risk that these carbon sinks may become emission sources; for example, due to fire.

Finally, we must introduce biofuels: these, unlike fossil fuels (e.g. petroleum), are renewable resources, since they are cultivated plants for use as fuels. Although they fail to remove CO2 from the atmosphere or reduce carbon emissions, they get to avoid this increase in the atmosphere. For this reason, they may not become a strict mitigation measure, but they can keep neutral balance of uptake and release. The problem is that they can lead to side effects on social and environmental level, such as increased prices for other crops or stimulate deforestation to establish these biofuel crops, what should not happen.

800px-Canaviais_Sao_Paulo_01_2008_06
Sugarcane crop (Saccharum officinarum) in Brazil to produce biofuel (Author: Mariordo).

Difusió-anglès

REFERENCES

 

Whale migration is changing due to global change

Results of a research that took place from 1984 to 2010 in the Gulf of St. Lawrence (Canada, North Atlantic Ocean) about changes in migration patters of whales due to global change have been published this March on Plos One. In this post, you are going to find a summary of this article.

INTRODUCTION

Global change (wrongly called climate change) is a planetary-scale change in the Earth climate system. Despite of being a natural process, in the last decades the reason of the changes is human because we have produced an increase of the carbon dioxide’s realise due to fossil fuel burning.

MIGRATION OF WHALES

Global change is a challenge for migratory species because the timing of seasonal migration is important to maximise exploitation of temporarily abundant preys in feeding areas, which, at the same time, are adapting to the warming Earth. Other driving forces are the use of resources like mates or shelter. This is the case of fin whale (Balaenoptera physalus) and humpback whale (Megaptera novaeangliae), which feed on a wide variety of zooplankton and schooling fish. This zooplankton grows due to an increase of phytoplankton, which grows for the increasing light and nutrients during summer. Remember that in this post you can read about the feeding behaviour of humpback whales. This is not the first time that it has been reported changes in migration species’ home ranges in both summer and wintering areas and alterations of the timing.

Fin whale (Balaenoptera physalus) (Picture from Circe).
Fin whale (Balaenoptera physalus) (Picture from Circe).

Humpback whale (Megaptera novaengliae) (Picture from Underwater Photography Guide).
Humpback whale (Megaptera novaeangliae) (Picture from Underwater Photography Guide).

It is observed a general pattern in migratory species: they use high-latitude summer regions to take advantage of high productivity and abundance of their preys and some of them reproduce during this period. Generally, long-distant migrants seem to adapt less well to climate change than short-distant migrants.

humpback whale migration
The case of humpback whale (Megaptera novaeangliae) migration. (Picture from NOAA).

Most baleen whales begin seasonal migrations from few hundreds to thousands of kilometres, alternating between low-latitude winter breeding grounds to high-latitude summer feeding grounds. The response of marine mammals to global change has been predicted:

  • More pole-ward distribution and more beforehand arrival in feeding areas to follow changing prey distribution.
  • Longer residency time in higher latitudes in response to enhanced productivity.

HOW IS GLOBAL CHANGE AFFECTING WHALE MIGRATION?

The article’s results show that fin and humpback whales arrived earlier in the study area over the 27 years of the study. Nevertheless, the rate of change of more than 1 day per year is undocumented. Both species also left the area earlier, as observed in other species. Humpback whale departure changed at the same rate as arrival, so it keeps a constant residency time. On the other hand, fin whales have increased the residency time from 4 days to 20 days. However, that increase is subject to small sample bias in the first two years and there is only weak evidence that fin whales increased their residency time.

Mean first and last sighting date in fin whale (Balaenoptera physalus) and humpback whale (Megaptera novaengliae) (Data from Ramp C. et al. 2015).
Mean first and last sighting date in fin whale (Balaenoptera physalus) and humpback whale (Megaptera novaeangliae) (Data from Ramp C. et al. 2015).

In addition, the results suggest that the region represents only a fraction of the potential summer range for both populations and both species just spend a part of the summer. What is clear is that both species showed the same behavioural adaptation and advanced their temporal occurrence in the area by one month.

Other studies have reported that gray whales (Eschrichtius robustus) have probably ceased to migrate annually in Alaska (Stafford K et al. 2007).

WHY ARE WHALES SHIFTING THEIR MIGRATION PATTERNS?

It seems that fin whale arrival in the Gulf follows the shift in the date of the ice break up and the sea surface temperature (SST) serves as a signal to the whales that it is time to move back into the Gulf. There was a time delay of 13-15 weeks between when this area became totally ice-free and their arrival. This has also seen in Azores, where fin and humpback whales arrive 15 weeks after the start of the spring bloom to feed on it when en route to high latitude summer feeding grounds.

The influence of SST in January in the Gulf may have triggered an earlier departure of humpback whales from the breeding grounds and thus earlier arrival in the Gulf.

These two species of whales are generalist feeders and their arrival in the Gulf is related to the arrival of their prey. The improvement of the temperature and light conditions and earlier ice break-up (together with higher SST) leads to an earlier bloom of phytoplankton followed by the earlier growth of zooplankton. Therefore, the earlier arrival of fin and humpback whales enables timely feeding on these prey species. A 2-weeks time lag between the arrival of fin and humpback whales lets humpback whales fed at a higher trophic level compared to fin whales, what reduces competition.

CONCLUSION

Global change shifted the date of arrival of fin whales and humpback whales in the Gulf of St. Lawrence (Canada) at a previously undocumented rate of more than 1 day per year earlier (over 27 years) thus maintaining the approximate 2-week difference in arrival of the two species and enabling the maintenance of temporal niche separation. However, the departure date of both species also shifted earlier but at different rates resulting in increasing temporal overlap over the study period indicating that this separation may be starting to erode. The trend in arrival was strongly related to earlier ice break-up and rising sea surface temperature, likely triggering earlier primary production.

REFERENCES

This post is based on the article:

  • Ramp C, Delarue J, Palsboll PJ, Sears R, Hammond PS (2015). Adapting to a Warmer Ocean – Seasonal Shift of Baleen Whale Movements over Three Decades. PLoS ONE 10(3): e0121374. doi: 10.1371/journal.pone.0121374

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Hands-free in the Pliocene

In the previous post we discovered the anatomical changes associated with bipedalism in early hominids and the relationship of the selection of this feature with climate change. Is bipedalism a trait that makes us human? What are the advantages over other quadruped animals?

WHAT IS THE PLIOCENE?

Since the origin of our planet, geologists have divided time into different divisions of millions of years: the eons (Archean, Proterozoic and Phanerozoic), which in turn are divided into different eras. The Phanerozoic (from 542 Ma to present) is divided into three eras, from oldest to newest: Paleozoic, Mesozoic and Cenozoic. In this link you can see  the major biological milestones for each epoch.

cenozoic
Cenozoic detail. Full image

The Miocene is the time when the hominoids appear, (Proconsul is the most famous genus) and in the Pliocene appears, among others, Australopithecus. Homo sapiens do not appear until the Holocene, a blink in the planet’s history, as they say.

Usually the climate changes that have been happening throughout the history of Earth, represent extinction, diversification and new species, and so does our evolutionary branch: many authors relate climatic fluctuations with milestones of hominins. If you are interested in this interactive you can investigate this issue.

slideshow_plate_tectonics_02
Position of the continents in the Miocene after the collision between the Eurasian and Indica plates. (Photo by The Burgess Shale)

One of these climatic changes (caused by the collision of the Eurasian and Indica tectonic plates,  giving rise to the Himalayas and changing wind currents) was responsible for the disappearance of large tracts of rainforest, giving way to a landscape shrub or savanna. Hominoids who stayed in the forest, led to the current nonhuman apes, while those who occupied the savannatrees mosaic led to hominins, our lineage. What are the advantatges of bipedalism in that landscape?

ADVANTATGES OF BIPEDALISM

  • Handsfree: the two free limbs can be used to transport food and offspring. You can reach fruit trees without stepping on them and later, will allow the manipulation of tools, hunting and cultural events.
  • Less heat: without offering the entire back surface to the sun, and separating the body from the hot ground, it allows cope better with high temperatures and survive with less water.
  • More energy: walking on two legs consumes less energy than walking on four. This allow walking longer distances with less food, which is important in an environment where you have to flee or find food constantly. We have a great strength to walk or run many kilometers compared with quadrupeds.
  • Best visual field: the eyes have a higher position and can detect potential predators over shrubs or drive them away with stones if necessary. It is also easier to spot food sources.
  • Intimidating appearance: upright posture appears to increase body size and can avoid confrontations with certain predators.
  • Better communication: the insertion of the skull with the spine, leaving enough space for the vocal cords allow, over time, the appearance of articulate speech. Although other apes had the same brain capacity to talk, morphologically it is impossible because of the structure of their vocal apparatus.
Algunas ventajas del bipedismo. (Ilustración de Karen Carr Studios)
Some advantatges of bipedalism. (Illustration by Karen Carr Studios)

DISADVANTAGES OF BIPEDALISM

  • Low speed: for short distances, running on two legs is slower than four, in case of an unexpected attack by a predator, the chance to escape decreases.
  • Back pain: the stress that suffers our spine and legs throughout life due to upright posture, is the most likely cause of back pain, knees, hips and feet that suffer a large part of the world population.
  • Birth complications: our birth canal is narrower due to the structure of our pelvis, plus the large size of the skull of the young, it causes more pain and complications in human births compared to other mammalian quadrupeds.
Canal del parto en una mujer (izquierda) y una chimpancé (derecha). Foto tomada de Jose Mª Bermúdez de Castro
Birth canal in a woman (left) and a chimpanzee (right). (Photo taken of Jose Mª Bermúdez de Castro)

Thus, despite the disadvantages, in a warm environment, rather arid and with few trees for shelter from predators, who survived were bipedal hominoids. We consider our bipedalism as a trait that makes us human, as it is unique among animals: only birds are fully bipedal -like some extinguished dinosaurs, and except the penguin -with clumsy gait, their spine is not perpendicular to the ground, like ours.

REFERENCES

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Lucy in the ground with diamonds

Surely one of the responsibles that you’re reading this post was the climate change that took place about 6 million years ago. The lifting of the Rift Valley caused a cooling and drying of sub-Saharan Africa, which favored the extension of the savannah at the expense of forests and the evolution of the first hominans who already walked by two feet. The most famous of them is undoubtedly Lucy. We encourage you to meet Australopithecus afarensis and the anatomy associated with bipedalism.

¿WHO WAS LUCY?

Just over 40 years ago, Donald Johanson discovered a partial skeleton (AL-288-1) 3.2 million old in Hadar, Ethiopia. It was the oldest hominan discovered and the bones belonged to an unknown species. At night, while celebrating the discovery with his team, the Beatles song Lucy in the Sky with Diamonds was playing in the cassette, and nicknamed the fossil remains. They belong to the species Australopithecus afarensis (Afar southern monkey).

Reproducción de Lucy del Museum national d'histoire naturelle, Paris. (Foto: autor desconocido, Wikimedia)
Cast of Lucy in the Museum National d'Histoire Naturelle, Paris. (Photo: unknown author, Wikimedia)

Currently A. afarensis is one of the best known early hominans, as it have been found remains of hundreds of individuals, males, females and young ones.

ANATOMY

The average height and weight of A. afarensis was 1.05 m and 29 kg for females and 1.51 m and 42 kg for males, significantly smaller compared to us. Brain volume was also small, 387-550 cubic cm (similar to a current chimpanzee). The arms and fingers were longer than ours, which allowed them to climb easily in the trees, and the legs, though shorter, had characteristics that allowed bipedalism (walking on two feet) completely. The forehead was narrow and jaws were located forward (prognathism), with a large space for jaw muscles. Their diet was mainly herbivorous.

Representación de Lucy por Elisabeth Daynès, con las huellas de Laetoli, en CosmoCaixa Barcelona. (Foto: Mireia Querol)
Reconstruction of Lucy by Elisabeth Daynès, with Laetoli footprint trails, in CosmoCaixa. (Photo: Mireia Querol)

ANATOMICAL FEATURES OF BIPEDALISM

A. afarensis already had the necessary adaptations to walk like us, though perhaps is not the older bipedal hominan: Orrorin tugenensis (6.2 to 5.6 million years) is aspiring to be one of the first members of the human race who walked upright .

skeleton comparison
Comparison between the skeletons of a current human (Homo sapiens), an A. afarensis and a chimpanzee (Pan troglodytes). (Photo: H. sapiens unknown author, A. afarensis John C. Phillips, chimpanzee Udo M. Savalli).
  • Foramen magnum: the spinal cord goes through an opening in the skull, the foramen magnum. In the chimpanzee is located in the back of the skull, while afarensis has it in the base, which allows a vertical backbone settle.
  • Backbone: lumbar and cervical area of the human backbone are more curved, we have a column with a S” shape. The center of gravity is in the midline of the foot and allows spinal flexion during walking, therefore when chimpanzees walk on two feet, stagger for balance because they have a straight spine.
  • Rib cage: A. afarensis still has a rather conical chest to accommodate a larger digestive system due to herviborous diet and better shoulder mobility to climb. H. sapiens have it shaped like a barrel, which facilitates the swing arm for better balance while walking and allows a better torso bending.
  • Pelvis: human pelvis is shorter and wider than other primates, to allow better mobility with the base of the backbone, but the birth canal is narrow.
  • Feet: A. afarensis toe, like ours, is aligned with the rest of the fingers, the sole is arched and a wide bead allows the foot to propel with the fingers and absorb shock when walking.
  • Femur: due to bipedalism the joint surface is wide and the femur is angled toward the center of gravity. In the chimpanzee femurs are shorter, less inclined and with lower joints.

LAETOLI FOOTPRINT TRAILS

Huellas de Laetoli, Tanzania. (Foto: Science Library)
Laetoli footprint trails, Tanzania. (Photo: Sciencephoto Library)

2.000 kms further south where Lucy was found, in Laetoli (Tanzania), Mary Leakey discovered in 1978 the oldest known biped trail (3.6 million years) of probably 4 hominans who walked through the open savannah, with traces of other extinct animals like the horse Hipparion, a bird, a baboon and a centipede. The tracks are laid down in the ashes of the volcano Sadiman and are attributed to A. afarensis. There are 69 footprints, some overlapping others intentionally, perhaps as a strategy to leave no trace. The big toe is parallel to the rest of the fingers and a deep footprint and the bead is well marked, which confirms a completely bipedal stride.

But why has it been so important bipedalism in the process of humanization, towards the emergence of Homo sapiens? We’ll find out in the next article on human evolution.

Representación de A. afarensis por John Gurche. (Foto: Chip Clark)

Rreconstruction of A. afarensis by John Gurche. (Photo: Chip Clark)

 

REFERENCES

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