Anthropogenic climate change is a real event. It’s already happening. An event that has provoked humanity with its activities and its emissions. The scientific consensus is resounding and solid. It is true that the climate is, by itself, a changing entity; what is relevant in the human-driven scenario is the magnitude of the change and its speed.
A gradual and slow climate change does not have to be problematic in any way ; species and ecosystems have time to adapt, to evolve. On the contrary, the few times in the earth’s history that sudden climatic changes have occurred, the consequences provoked mass extinctions. Events such as those that occurred at the end of the Permian, Triassic or Cretaceous are proof of this.
But today’s climate change is very different from those, and not just because it’s being caused by a single species, but because it’s happening faster than anything else in Earth’s history. We are achieving in little more than two centuries what, in the past, happened in millennia or tens of millennia. Even in the most catastrophic cases.
What climate change can cause covers a wide range of consequences. The sea level will rise several meters. Infrequent extreme weather events will become more frequent, and more extreme. Allergies will change. Species will be forced to move elsewhere.
And like them, human populations. Sooner rather than later, there will be talk of climate refugees. Climate change, after all, is still the main driver of global change.
But the most serious consequence of this phenomenon may have a much more disastrous character, if possible. Today, World Wildlife Day, we talk about the risk to the biosphere. We speak of a collapse of biodiversity.
The collapse of biodiversity
The constant advance of anthropogenic climate change implies an increase in risks for biodiversity , and future projections are not encouraging. The data indicates that, indeed, if nothing changes, a catastrophic event will happen for the wildlife of the plane. The hard part is knowing when. The predictions that can be made for the future contain a huge number of variables where small changes in the initial data can significantly change the results.
The most ambitious and comprehensive work to date was led by Christopher Trisos of the University of Cape Town, published in April 2020. In that work, they made temperature and precipitation projections spanning the years 1850 to 2100, and the applied to more than 30,000 species, marine and terrestrial. Each species has a thermal niche , which is the optimal range of temperatures for its existence; When a species is exposed for a long time to temperatures beyond the thresholds of its niche, it becomes endangered.
Based on these data, in this research they estimated the percentage of species that would be exposed outside their thermal niche in different parts of the world. For this they contemplated three scenarios; one in which a strong mitigation of the effects of climate change is established immediately ; another intermediate in which a slight mitigation is established; I another high-emission extreme, where basically nothing is done to avert disaster .
If nothing is done and we continue to emit as before, without trying to find a solution, 100% of the species in the Amazon region would be out of their thermal niche in 2053. The coral triangle —in Indonesia, Papua New Guinea and even the Solomon Islands—would also have all of its biodiversity exposed by 2065, and the Congolese jungle by 2080.
However, desert regions such as the Gobi would be much less impacted ; only 20% of its species would be exposed there. Globally, up to 71% of the planet’s species would be exposed, happening to a greater extent and more abruptly in the seas. The worst effects would be between the two tropics.
If this prediction comes true, there is no doubt that we would be facing the sixth great mass extinction in the history of the planet.
What if we start acting now?
The exposed catastrophic prediction is based on an extreme premise: do nothing to avoid disaster. What do the mathematical models say if we change the scenario, and go to the other extreme? Can a drastic change of best effort to mitigate the effects of climate change serve to avoid the collapse of biodiversity? Can we save wildlife? That possibility was also explored.
To begin with, the most optimistic scenario delays the exposure of species at greatest risk for up to six decades. In this hypothetical situation, in the year 2100 we would have less than 30% of terrestrial species and less than 20% of marine species outside their thermal niche. In addition, this 60-year delay could be very useful, not only to make it easier for species and ecosystems to adapt to the new climate , but also for human societies to do so, since they depend on them. Because many believe that wildlife is an accessory, that we can live without it, when in reality we are deeply dependent on it.
In the current circumstances, although the situation is serious, there is still room for manoeuvre ; cutting emissions sharply and quickly can buy time. It is true that species have a strong phylogenetic inertia, and it is difficult for them to change the ecological niche of their ancestors. It is difficult to cross a threshold that has remained immobile for thousands or even millions of years. But the more time we give them, the better they will adapt to these new conditions, which will come.
Preventing many species from being exposed outside their thermal niche, and delaying it from happening to those for which it is already inevitable, is possible, but requires rapid and global action to reduce greenhouse gas emissions. The ordinary citizen can carry out many and very noble actions, but the main responsibility does not fall on him. It is the great powers and industries that are emitting the most and those that should look up as soon as possible and see what is to come, before it falls on us. Today, World Wildlife Day, could be a good day to start doing it.
REFERENCES:
Cook, J., Oreskes, N., et al. 2016. Consensus on consensus: a synthesis of consensus estimates on human-caused global warming. Environmental Research Letters, 11(4), 048002. DOI: 10.1088/1748-9326/11/4/048002
Marques, L. 2020. Collapse of Terrestrial Biodiversity. En L. Marques (Ed.), Capitalism and Environmental Collapse (pp. 247-273). Springer International Publishing. DOI: 10.1007/978-3-030-47527-7_10
Trisos, C. H., Merow, C., et al. 2020. The projected timing of abrupt ecological disruption from climate change. Nature, 580(7804), 496-501. DOI: 10.1038/s41586-020-2189-9
