Arxiu d'etiquetes: atmosphere

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 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