Arxiu d'etiquetes: global change

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.

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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.

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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.

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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).

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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.

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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.

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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.

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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.

Difusió-anglès

Migration in danger! The disappearance of the monarch butterfly

Generally, we tend to think of migration as an event exclusively linked to complex organisms (like mammals or birds). But there are always exceptions: the North American populations of the monarch butterfly (Danaus plexippus) cover a distance of almost 5000km (more than some complex animals!) in order to reach their hibernation areas, where there can be concentrated thousands of specimens during the winter. Unfortunately, the migration phenomenon depend on many factors that are being damaged by anthropogenic pressure nowadays, so that the future of these populations and also their migration are in danger.

Throughout this article, you will learn some of the most curious biology traits of these organisms, the main causes that could be endangering their populations and the consequences that this would entail.

INTRODUCTION

The monarch butterfly (Danaus plexippus) is a butterfly of the Nymphalidae family. It’s also probably one the most well-known butterflies of North America due to its long migration, that their specimens perform from the north of EEUU and Canada to California coast and Mexico, covering a distance of almost 5000km to reach their hibernation areas. It’s, by far, the insect that performs the widest and large migration of all.

Specimen of monarch butterfly (Danaus plexippus) with its typical color pattern: white, black and orange (Picture by Peter Miller on Flickr, Creative Commons).

Although the North American populations of this species are the most known worldwide due to their migration pattern, there are also monarch butterflies in some Atlantic islands (Canary islands, Azores and Madeira), and sometimes also as eventual migrators that reach the coasts of Western Europe (United Kingdom and Spain). Moreover, they were introduced in New Zealand and Australia during the XIX century.

LIFE CYCLE

The life cycle of this species is very unique. First of all, they’re considered specialist butterflies: they lay their eggs exclusively over plants of the Asclepias genus (also known as milkweeds), and their newborn caterpillars (which are black, white and yellow striped) feed only on these plants. This is a very interesting fact, because the plants of this genus contain cardiac glycosides that are progressively assimilated by the caterpillar tissues, which let them to acquire a disgusting taste that prevents them to be predated. This taste will last during their adult phase.

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Caterpillar of a monarch butterfly (Picture by Lisa Brown on Flickr, Creative Commons).

Once completed the larva phase, the metamorphosis take place so that the caterpillars become adult butterflies colored in black, white and orange. Both caterpillar and butterfly color patterns carry out a communicative function: it’s a mechanism to warn other animal of their toxicity, fact which is known as aposematic mimicry (this phenomenon is very frequent in a lot of group of animals, even in mammals).

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Phases of the metamorphosis of the monarch butterfly (Picture by Steve Greer Photography).

The adult phase also has some particularities: during the mating season (April-August) some generations of adults are generated, and each of them has a life expectancy of a few weeks, more or less. Then, an awesome event takes place: the butterflies of the generation born at the end of August (when temperatures get low and days became shorter) stops the maturing process of their reproductive organs (phenomenon known as diapause) so they can spend their energy on enlarging their life expectancy to 9 months. This generation is known as “Methuselah generation” due to its longevity.

The increase of their longevity allows this generation to cover the long distance required to reach the hibernation areas during the autumn (Mexico and California coast) and then to come back to the north of America at the end of the winter.

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Hundreds of monarch butterflies flying over the place called ‘El Santuario ‘El Rosario” (Mexico) (Picture by Luna sin estrellas on Flickr, Creative Commons).

A ROUND TRIP: THE GREAT MIGRATION

Although the monarch butterfly isn’t only located in North America, there is no evidence nowadays showing that the other populations of monarch butterflies do such a long migration. It’s believed that the fact that only these populations of butterflies go on a trip this long is due to the wide spreading of plants of the Asclepias genus over all North America that took place in the past. Scientists suggest this event allowed the monarch butterflies to spread progressively to the south.

WHICH PLACES DO THE BUTTERFLIES VISIT?

A migration is always a complex process. In this case, the migration to the south is divided into two simultaneous migrations:

  • The east migration: this trip is made by those butterflies that fly from the east of the Rocky Mountains, South of Canada and a big part of USA to the central part of Mexico (90% of all the monarch butterflies located in North America go on this trip).
  • The west migration: this trip is made by those butterflies that fly from the west of the Rocky Mountains, South of Canada and a little part of USA to the California coast (10% of all the monarch butterflies located in North America go on this trip).

Migratory patterns of the monarch butterfly in North America (round trip) (Sources: Monarchwatch.org y Monarch Alert).

Once in the winter habitats, the butterflies plunge into a lethargic state until the next spring, when they become sexually active and start mating before heading again to the north.

It’s a very surprising event seeing all the butterflies sleeping together and covering all the plants and trees of the winter habitats!

Thousands of butterflies gather over the vegetation (Picture by Carlos Adampol Galindo on Flickr, Creative Commons).

PROTECTED AREAS

There exists a lot of protected areas all over the places where the butterflies go through.

One of the most important protected areas is the Monarch Butterfly Biosphere Reserve (Mexico City), which is considered a World Heritage Site by the UNESCO since 2008.

Monarch Butterfly Biosphere Reserve (Picture by Michelle Tribe on Flickr, Creative Commons).

And why are these butterflies so protected? Besides the fact that their migration pattern is considered an incredible phenomenon, they are pollinators that contribute to the pollination of the wild flora and also of the crops of North America.

THE ‘QUEEN’ IS IN DANGER!

Although there exists a huge effort to protect them, the migratory phenomenon of the North American monarch butterflies is in danger nowadays due to the anthropic pressure, which could also put their populations at risk in the future.

According to the data generated by the WWF, the surface of the winter habitats occupied by these butterflies has decreased 94% in 10 years, going from 27,48 acres occupied in 2003 to only 1,65 acres in 2013. This is the lower value registered in the last 20 years.

Decresing of the surface occupied by the monarch butterflies in the winter habitats (Data form WWF website).

Even though the surface occupied by these organisms has been fluctuating over the years as a part of a natural process, this pronounced decreasing that has taken place in only a few years suggests that butterflies are stopping their annual migrations to the south.

Total occupied area by the butterflies in their winter habitats since 1993 to 2013 (WWF-Telcel-CONANP).

This recession has also been registered in other species of butterflies at different emplacements all over the world, so there must exist some kind of factor in common with the ones affecting the North American monarch butterfly populations.

WHAT COULD BE THE MAIN CAUSES OF THIS RECESSION?

According to the WWF, the main causes that could being putting in danger the migration process of the monarch butterflies are:

  • The reduction of the surface occupied by plants of the Asclepias genus: as we said above, the caterpillars feed exclusively on these plants. But the use of certain herbicides and the changes on the rain patterns could being limiting their dispersal over a big part of North America.
  • Deforestation: cutting down trees massively and the subsequent desertization could being reducing their winter habitats.
  • Extreme climate: the global change, which entails changes in temperature and rain patterns, could being putting at risk the survival of adult butterflies, preventing them to reach the longevity required to carry out complete migrations.

WHICH EFFORTS ARE MADE TO PROTECT THESE POPULATIONS?

As I said above, monarch butterflies are an essential part of the pollination net of North America and also iconic insects, so there exists a big interest on protecting them.

Nowadays, most of the protected areas of North America are making a big effort to improve the quality of their habitats. Among them, the Monarch Butterfly Biosphere Reserve (Mexico) along with the WWF are trying to restore the woods where butterflies hibernate and also promoting a sustainable tourism (enter this link to see more information).

 .            .            .

The case of the monarch butterfly is only one of a huge list of animals in danger. Nowadays, a lot of animals with complex migration patterns and wide spreading areas are suffering similar pressures, mostly of them with an anthropogenic origin. There’s still so much work to do, and it depends on all of us.

REFERENCES

Main picture by Carlos Adampol Galindo on Flickr.

Difusió-anglès

Why are beaches disappearing?

Probably you have listened that our beaches are disappearing. Why do beaches disappear during storms? Why do beaches not regenerate naturally? There are several causes that explain the regression of line coast, having all of them a human origin. In this article, I want to explain which are the reasons of the regression of beaches and which are the possible solutions to this problem. 

INTRODUCTION

Beaches are zones placed between land and sea where sediments accumulates. Not only are they a place where people can enjoy, but also a habitat for many animal and plant species and with a defensive function.

FUNCTIONING OF A BEACH

On beaches, there is a sediment accumulation from fluvial flows. Swell, on the one hand, causes a displacement of these sediments through the coast (with more or less intensity), what is known as longitudinal littoral transport. To maintain a beach, the amount of sediments that disappear from a beach have to be the same that those that are added. On the contrary, the beach reduces (prevails the erosion) or increase. It has to be added the transversal littoral transport, which consists on the swell moving sediments from emerged beach to underwater beach, or backwards. Wind, at the same time, can produce an accumulation of sediments in the more interior part of the beach, creating dunes.

Funcionament dinàmic de la costa (Imatge: Directrices sobre Actuaciones en Playas)
Dinamic functioning of coast  (Picture: Directrices sobre Actuaciones en Playas)

So, a beach is working correctly if:

  • There is a stable source that contribute with the necessary sediments to make a beach.
  • There is a free movement of the sediments through the coast and in the transversal way.

Therefore, the main problems of regression of beaches are due to a modification of one or both factors.

WHY ARE BEACHES DISAPPEARING?

Now, it’s time to talk about the reasons why beaches in our littoral are being reduced or in regression. As mentioned above, these can be classified in two types: causes that reduce the source of sediments and causes that impede their movement.

WHICH ARE THE CAUSES OF THE REDUCTION IN THE CONTRIBUTION OF SEDIMENTS?

Construction of dams, with the aim of regulating the flow of rivers, is one of the main causes of the regression of beaches. The construction of dams produce a retention of sediments in the reservoir of water, what impedes their movement river downhill and, for this reason, their arrival in coast. It is this accumulation that explain that the useful life of dams is just 55-60 years. To give an example, in the Ebro Delta (Catalonia) arrives every year 200,000 tonnes of sediments, 10 times less than what is necessary to maintain the delta constant and 100 times less than what arrived in 20th Century.

Les preses produeixen l'acumulació de sediments i, per tant, la regressió de les platges (Foto extreta de Adasa).
Dams produce an accumulation of sediments and, for this reason, the regression of beaches (Picture from Adasa).

The urbanization of littoral zone close to beaches impedes the mobilization of sediments. Without going any further, due to the increase of the interest in the last decades of the population to coast, there have been a massive construction of promenades behind beaches, followed by important flat blocks. This has supposed the destruction of dunes and their plants mostly in all the littoral. Dunes are important zones of accumulation of sediments, so they constitute a sediment reservoir, it is that after a storm, wind can sweep along sand form this ecosystem and, thus, it can naturally regenerate the beach. Moreover, dune’s vegetation give stability to the beach since it affixes the sand and impede its erosion.

La construcció de passeigs marítims sovint va acompanyada de la destrucció de les dunes, el que té un efecte negatiu sobre les platges (Foto de Ayuntamientos.org)
Construction of promenades is usually accompanied by the destruction of dunes, that has a negative effect on beaches (Picture from Ayuntamiento.org)

There are other explanations, like the occupation of the surface of rivers by urbanizations or the removal of sand and gravel, among others.

As we have seen with dunes, these could be a source of natural regeneration of beaches. We have to had also in consideration that the destruction of seagrasses (like Posidonia) due to the urban development, bottom trawling, construction of harbours, piping and sewage pipes and the increase of anchors helps that the transported sand during a storm isn’t retained in the zone close to the beach, so this sand don’t naturally return by swell to the original position.

La destrucció de la Posidonia afavoreix l'erosió de la costa (Foto de Periodico de Ibiza).
Destruction of Posidonia contributes to the erosion of coast (Picture from Periodico de Ibiza).

WHY CANNOT SEDIMENTS BE SPREAD THROUGH COAST?

Again, the occupation of beaches by buildings and other infrastructures explains why sediments can’t be spread through coast with freedom. Anyway, it is important to mention the construction of maritime structures. Effectively, we are referring to the construction of dikes, breakwaters and harbours, that constitute a barrier that produce the accumulation of sediments in the opposite side of the current direction, while it produce erosion downhill.

Les obres marítimes alteren la dinàmica del transport de sediments (Foto de Cyes).
Maritime constructions modify the dynamics of sediment transportation (Picture from Cyes).

To all this causes, we have to add the global change that, due to the rise in the sea level, is producing the disappearance of the littoral because it is sinking.

WHICH ARE THE SOLUTIONS?

There are several possible solutions to face beach regression, but all of them have their problems:

  • Artificial regeneration of beaches with marine or terrestrial sediments. The dredging of sea floor has a negative impact on plants and animals of the zone, specially if these areas have seagrasses like Posidonia. When the origin is terrestrial, it usually come from quarries (with the posterior crushing), so its touch is not pleasant and it produces the destruction of mountains.
  • Construction of maritime structures like dikes and walls. These are not free from problems because they produce the erosion downhill.
  • Elimination of obstacles that stop the sediments or the free circulation.

Sometimes, the most prudent solution, in the case of not being any interest for population, is to leave the beach to its luck. It means to leave the natural evolution of the beach happen.

REFERENCES

Difusió-anglès

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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And the waters went up

This week the topic is a worldwide problem favoured by human action, which is one of the several consequences of global change. Effectively, I’m talking about sea-level rise.

INTRODUCTION

Since the end of the last ice age to the present day, sea-level has risen by about 125 meters. The causes of this sea-level rise have both a natural and human origin, despite the human-induced greenhouse effect is intensifying this process.

WHAT IS IT AND WHICH ARE THE CAUSES?

The sea-level rise is one of the worst consequences of global change. The coastal areas are the most densely populated of the world, so two thirds of the Earth population live in the first 8 km from the coast. They are especially vulnerable to the impacts of global change due to the presence of major agricultural zones, conurbations and heritage sites.

Sea-level is determined by natural and human-induced green house effect. Specialists distinguish between:

  • Eustatic causes: this refers to the water mass being added to the oceans. An example is the sea-level rise following the melting of large glaciers at the end of ice ages.
  • Isostatic causes (generally tectonic): it refers to the sinking or rising of Earth’s crust due to its weight. On the one side, during glaciations, the increase of ice sheets on the crust causes an increase of the weight, causing its sinking. On the other side, during the warmer periods (interglacial), the melting of the ice means a reduction of weight and, for this reason, the curst rises. This phenomenon has regional effects.

TO WHAT EXTEND SEA LEVEL WILL RISE?

Sea level can change by 10 meters or so within the course of a few centuries and can fluctuate by more than 200 meters over millions of years. During glacial periods, sea level reduces due to the formation of big ice sheets on the continent, while in the interglacial periods its melting causes a rise in the sea level.

Nevertheless, if we compare the sea-level rise of this last century with the almost constant level of the last 6000 – 8000 years, we can observe a rise of 18 cm in just 100 years and 3.2 cm in the last decade. Experts believe that between 15 and 50% of sea-level rise is attributed to the temperature-related expansion of seawater, that 25 – 45% is caused by the melting of mountain glaciers outside the polar regions, and between 15 and 40 per cent is caused by the melting of the Greenland and Antarctic ice caps.

Sea level will significantly rise by the end of this century, although the precise extend to which it will increase is uncertain. The Intergovernmental Panel on Climate Change (IPCC) considers a rise of up to 1 meter during this century (dark green shading in the picture), while other researchers forecast a rise of more than 180 cm (light green shading in the picture). If most of the ice sheets in Greenland and West Antarctica melt, sea level could increase by as much as 20 meters in the following 1000 years in a worst-case scenario. The last time that the Earth had a similar temperature to the predicted in 2050, sea level was 4 meters above the nowadays level.

Sense títolFuture scenarios of the sea-level rise. In dark green, the IPCC's forecast and in light green the worst case. (Origin: Future Ocean)

REFERENCES

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