Mass Extinction Forecast With 6C Temperature Rise

Paul Brown, Climate News Network

By Paul Brown, Climate News NetworkThis article originally appeared at Climate News Network.

LONDON — Animals, including humans, will shrink in size to survive in a warming world, according to scientists studying the last time the planet’s temperature rose rapidly by 6°C. What scientists call dwarfism was the successful strategy to avoid starvation for a large range of species including horses, many insects and even earthworms. The widespread response was partly to do with the heat but mostly because many plants became less nutritious, forcing mammals and insects to eat far more to survive.

In the next 100 years the combination of more carbon dioxide in the atmosphere and increased temperature could be “catastrophic” for an overpopulated world, according to one of the scientists involved. With food supply drastically reduced, evolutionary forces suggest hobbit-sized humans who needed to eat less would have the greatest chance of survival. These findings are the work of an international group of 30 scientists looking at the vast fossil deposits in rock strata in Wyoming in the US, charting the period 55 million years ago when the Earth’s temperature rose suddenly – as it is expected to do this century.

On that occasion it took 10,000 years for the temperature to rise by 6°C. There were mass extinctions, but the timescale gave some plants and animals time to adapt and move north and south to survive. Many species evolved quickly – dwarfism being one of the most widespread and successful strategies.

The project, entitled the Bighorn Basin Coring Project, involves scientists from the US, the UK, Germany and the Netherlands. It is a United States National Science Foundation-funded project, aimed at understanding what happened the last time the Earth warmed and the consequences for the planet this century. The scientists leading the project are Will Clyde (University of New Hampshire), Philip Gingerich (University of Michigan) and Scott Wing (Smithsonian Institution).

What worries the scientists is that this current warming period will take as little as 200 years, if the Intergovernmental Panel on Climate Change is correct. This gives many long-lived species, for example trees, no time to evolve and migrate. Even mammals will struggle to move to new areas, because man has placed farmland and cities in the way.

Rapid warming leaves few choices

The result will be mass extinction, and for the survivors, humans, animals and insects, there will be a scramble to eat a diminishing and less nutritious food supply. Lower plant nutrition is caused by higher atmospheric carbon dioxide concentrations, rather than temperature itself. Plant growth experiments have shown that concentrations of both nitrogen and the protein Rubisco, which regulates carbon dioxide fixation, decrease under higher CO2 conditions, making many plant tissues less nutritious.

To get the same calories herbivores would have to eat more plant matter. Humans would be forced to grow more crops to get the same nutrition from food and spend more time eating it. Farm animals would also get smaller in response, making meat more difficult to obtain. Competition from insects eating food crops would be fierce.

Dwarfism is again expected to be a successful strategy for the survivors, enabling humans, animals and insects to mature earlier with less food and so reproduce before they starve. The researchers’ findings show that earlier optimism that increased carbon dioxide in the atmosphere would have a fertilization effect, allowing food plants to grow quicker in a warmer world, is more than countered by a loss in nutrition. For an overcrowded world this could be disastrous.

Dr Phillip Jardine, one of the scientists involved, is a research fellow at the School of Geography, Earth and Environmental Sciences at Birmingham University, UK. Giving a lecture at the Geological Society of London he said this period of warming, known as the Paleocene-Eocene Thermal Maximum, led to catastrophic extinctions of life in the deep oceans, partly because of increased acidification and partly through lack of oxygen. On land many plants and animals also died out.

However, because the warming took place over 10,000 years, many plants and insects were able to adapt, migrating north to avoid the heat or evolving to new forms. Alligators, unimpeded by dams, were able to migrate using natural waterways and lived successfully in the Arctic Circle. In the tropics numerous new species emerged. On the Gulf Coast of America, for example, 20% of species died out but were replaced by others moving in from elsewhere.

Afterwards Dr Jardine was asked by the Climate News Network what effect a 6°C increase would have on the planet currently if not enough action to curb emissions is taken. “For me this just shows how pervasive the impacts of altering the global carbon balance really are”, he said. “Even if future climate change isn’t a convincing enough argument to decrease carbon emissions, increasing atmospheric CO2 concentrations has a very real possibility of reducing the viability of our own food supplies, by compromising the base of the food chain for ourselves and the animals that we farm and eat.

“If we acknowledge the presence of increasing temperatures then we have an additional factor that we would expect to decrease further the size of our farmed animals, and thus the amount of food that we can take from them. I would say that the impacts of this on a large and growing human population could be catastrophic, especially in the developing world and when changes in other resources, for example water, are factored in as well.”

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