Extinctions inevitable

How many times have you read or heard comments from deniers that animals, plants and fungi will adapt to new environments or evolution will provide new capabilities as the climate changes? I know a number of denier dens like to highlight scientific papers where researchers have studied the effect of climate change on a particular organism where the result has been neutral or positive, and use this as “evidence” that everything will be ok.  CO2 Science has even compiled a list of papers on aquatic organisms.

I am more than happy to concede that some individual species will cope with climate change and some will actually benefit,  but what these studies don’t do, is look at ecosystem responses and the potential for ecosystem collapse. In studies of response to environmental disturbance, generally, ecosystems respond well to and actually require low to middle levels of disturbance. Disturbance keeps ecosystems healthy by facilitating a whole range of processes from nutrient cycling to niche partitioning. The end result is usually high levels of biodiversity. Think of rainforests with the occasional tree falling over. When disturbance is high (acute or sustained) generalist species, those with a wide range of tolerances, outcompete specialist species and the end result is low biodiversity and/or altered ecosystems. Think of a rainforest after a cyclone (acute) or desertification of rangelands (sustained).

Anthropogenic climate change is starting to create both acute and sustained disturbances in natural ecosystems resulting in latitudinal and altitudinal range shifts in tens of thousands of species as well as phenological adjustments. This in turn leads to changes in the biodiversity and function of ecosystems as they adjust to changes in niche fulfilment and abandonment with generalists coping better than specialists. So, what will be the fate of individual specialist species?  Will they be able to adapt or evolve quickly enough to adjust to the rapid rate of climate change we are experiencing? Being specialists, we can rule out adaptation. That leaves evolution.

What I have found amongst many non-scientists who have limited knowledge of biology, is a failure to appreciate timescales. As humans, we tend to measure time against our own lifespans. The concept of evolutionary timescales is lost. It is very difficult to observe evolution by natural selection in species as it can take hundreds to thousands of generations to bring about tiny changes that may result in some favourable outcome but of course evolution is blind and subject to chance. There is no guarantee that species will have the genetic mutations within a population that will allow survival in a changing environment anyway. When environmental change happens slowly, the chance that beneficial genes will evolve is greatly improved.

So, will species evolve quickly enough?

Research undertaken by Ignacio Quintero and John Wein, from the University of Arizona, reveals that in order to avoid extinction due to anthropogenic climate change, a large number of vertebrate species will have to evolve 10,000 times faster than they have in the past.

“We found that on average, species usually adapt to different climatic conditions at a rate of only by about 1 degree Celsius per million years, but if global temperatures are going to rise by about 4 degrees over the next hundred years as predicted by the Intergovernmental Panel of Climate Change, that is where you get a huge difference in rates. What that suggests overall is that simply evolving to match these conditions may not be an option for many species.” Dr John Wein

For a more detailed report on this study, go here.

For an excellent paper on predicting the impacts of climate change, go here.

Here is the paper Quintero and Weins paper…

Quintero & Wiens (2013) Rates of projected climate change dramatically exceed past rates of climatic niche evolution among vertebrate species. Ecology Letters DOI: 10.1111/ele.12144

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