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article imageHuge population drift augurs as climate change alters ecosystems

By Robert Myles     Oct 10, 2013 in Environment
Potsdam - Climate change is likely to transform landscapes worldwide, affecting most of Earth’s forests and agriculture — and it isn’t a far future scenario, says a new report. Profound changes in the world’s ecosystems could happen less than 90 years hence
In excess of 80 percent of Earth’s ice-free landmass runs the risk of experiencing fundamental changes in its ecosystem by 2100, according to a new report by researchers at the Potsdam Institute for Climate Impact Research and Humboldt University in Berlin, both Germany.
On the findings of their research, one of the report’s authors Sebastian Ostberg, a geo-ecologist at the Potsdam Institute, commented, "Essentially, we would be leaving the world as we know it."
Ostberg and his co-researchers studied the critical impact of climate change on Earth’s land-mass. Their results were published on Oct. 8, in Earth System Dynamics, an open access journal of the European Geosciences Union (EGU).
The researchers go on to warn that unless steps are taken to ensure that global warming does not exceed 2° Celsius above pre-industrial levels then, "nearly no area of the world is free" from the risk of climate change substantially re-shaping the world as we know it.
The wide range of changes to ecosystems the report predicts read as a catalogue of disasters, but on a barely imaginable global scale. Long-established boreal forests, also known as taiga, are at risk of being transformed into temperate savannahs. Boreal forest, principally made up of conifers, accounts for around 17 percent of Earth’s land area. In contrast, areas of tundra, in currently frozen Arctic regions, could see trees growing. Further south the world’s rainforests could see die-back.
All three examples presently constitute some of the Earth’s most important carbon sumps, with massive amounts of carbon locked up in the form of vegetation or in frozen ground. In the case of the tundra, where ground is permanently frozen, thawing on a massive scale would also release vast amounts of methane into Earth’s atmosphere. As a greenhouse gas, methane is 20 times more potent than carbon dioxide.
Such Earth-changing dislocation and relocation of ecosystems would have knock-on effect on food and water security, affecting humanity as a whole. Couple the predicted ecosystem changes to rising sea-levels and a likely increase in the frequency of extreme weather events, and a doomwatch scenario isn’t wide of the mark.
The Earth System Dynamics study demonstrates that up to 86 percent of the remaining natural land ecosystems worldwide could be at risk if humanity continues on its present path of delay and dither when it comes to putting in place effective restrictions on carbon emissions. The authors point out that the 86 percent figure quoted represents the total land-mass that could be at risk if global temperature increases by 5° Celsius by 2100. They go on to say that it’s unlikely all these areas would be affected. The 86 percent figure therefore represents the worst-case scenario if each climate prediction model turned into reality.
The climate models were based on assumptions that over the next 90 years or so up to 2100, global average temperature will be 4° to 5° Celsius warmer than in pre-industrial times. As the authors highlight, given that many countries' are dragging their feet when it comes to committing to binding emissions cuts, such a level of warming is entirely possible come the end of this century.
Even if, by some miracle, humanity manages to limit global warming to 2° Celsius, the researchers still have a stark warning. In that scenario, around one-fifth of land ecosystems would undergo at least moderate changes. The areas most affected would be those at high altitude and high latitude, nearer Earth’s Poles.
Looking at how the range of global temperature increases may affect the world's population, even if global warming is limited to 2° Celsius above pre-industrial levels, 500 million people could be subject to increased water scarcity. That may be optimistic based on current compliance with carbon emissions targets. The numbers affected would grow by a further 50 percent if there is no cut soon in greenhouse gas emissions — meaning a population more than twice that of today’s United States, short of food and short of water. Not only that, the extra 750 million or so, thirsty and starving, would be in addition to those unfortunate enough to find themselves in that situation in 2013. It's unlikely all these people would stay in the one place so large populations movements, on a scale never before imagined, could be in prospect.
The prediction models
Climate prediction and modeling is notoriously tricky. To get round his problem, the German researchers looked at more than 150 different climate scenarios, examining ecosystem change in almost 20 different climate models for varying amounts of global warming.
Co-author, Professor Dr. Wolfgang Lucht, co-chair of the research domain Earth System Analysis also at the Potsdam Institute, said, "Our study is the most comprehensive and internally consistent analysis of the risk of major ecosystem change from climate change at the global scale.”
Until now, few studies have examined the global impact of rising temperatures on ecosystems, due to the sheer complexity and inter-linkage of such ecosystems. As Professor Lucht put it, "Comprehensive theories and computer models of such complex systems and their dynamics up to the global scale do not exist."
Sebastian Ostberg explained that to obviate this problem, the research team measured simultaneous changes in the biogeochemistry of terrestrial vegetation and the relative abundance of different vegetation species. Ostberg explained,
"Any significant change in the underlying biogeochemistry presents an ecological adaptation challenge, fundamentally destabilizing our natural systems." explains Ostberg.
The researchers set about this by seeking to define parameters that would measure the difference between present and future ecosystems. At its simplest, a parameter would gauge the variables needed to bring about changes in vegetation — trees to grass as in the example above relating to boreal forest. The variables included the amount of carbon locked up in vegetation and frozen soil in permafrost regions as well as freshwater availability.
"Our indicator of ecosystem change is able to measure the combined effect of changes in many ecosystem processes, instead of looking only at a single process," said Ostberg, who hopes the new analysis can contribute to informed choices in negotiating climate mitigation targets, as well as forward planning to adapt to unavoidable changes brought about by climatic factors.
The research, entitled 'Critical impacts of global warming on land ecosystems' can be downloaded in PDF form from Earth System Dynamics.
More about Ecology, Ecosystems, Population growth, population movement, Climate change