The study found that even the most widespread and globally common species will not escape the detrimental impacts of climate change.
Climate change mitigation essential for even the most common species
30th August 2013
Anna Taylor takes a closer look at the worrying findings of a recently published study which, unusually, chose to assess potential climate change mitigation scenarios on the more widespread and common species found on our planet.....
The date of peak emissions is more important than the overall amount in terms of reduced impacts
It is well known that climate change will impact a great many species and ecosystems. The ranges of many species will change, ecosystem services will be disrupted, and biodiversity will be lost. But a new study has asked previously overlooked questions: What will happen if we try to stop climate change? What benefits would this bring in terms of avoiding biodiversity loss? And what will happen if we do nothing?
The Intergovernmental Panel on Climate Change estimates that, should temperatures reach two to three degrees above pre-industrial levels, 20-30% of species would be at increasingly high risk of extinction. With many species already endangered due to habitat loss, over-hunting and other anthropogenic factors causing their decline, climate change could well be the final nail in the coffin if their habitats become unsuitable as temperatures rise.
This recent study, published in the journal Nature Climate Change, conducted a comprehensive analysis of 48,786 animal and plant species throughout the world. The team of scientists wanted to find out how each of these species' ranges would change depending on what action we take to prevent climate change. This included what would happen to them if we take no action at all, their baseline scenario in which global temperatures reach 4°C above pre-industrial levels by 2100.
Of the total number of species studied, 80% currently have ranges spanning over 30,000 km2 - rather than focusing on rare species, the scientists chose to examine the impact of climate change mitigation on widespread, common species that are less likely to face extinction (and less likely to be studied) than those with smaller ranges.
The analysis showed that, without mitigation, 34% of animals would lose half or more of their climatic range. For plants, 57% would lose more than half of their current ranges, with negative impacts for those animals that rely on them for food. By comparison, only 4% of animals would benefit from climate change by gaining more than half of their range, and no plants at all would benefit, leading the scientists to surmise that climate change will "overwhelmingly result in a sizeable reduction of climatically suitable ranges for a large number of species."
The loss of common and widespread species raises serious concerns, as the study notes that even small declines in such species can "significantly disrupt ecosystem structure, function and services." Dr Rachel Warren from the University of East Anglia, who led the study, explains: "There will be a knock-on effect for humans because these species are important for things like water and air purification, flood control, nutrient cycling and eco-tourism."
The species most at risk was revealed to be plants, and the already beleaguered amphibians and reptiles due to their lower long-term dispersal rates. The study's projections suggest that amphibians will be the hardest hit, with 50% losing over half their range. The impacts of climate change will also hit certain parts of the world harder than others. The climate of Sub-Saharan Africa, Central America, Amazonia and Australia will become particularly unsuitable for animals and plants, with North Africa, Central Asia and South-eastern Europe also projected to experience major plant losses.
Despite its dire predictions, the study does contain some good news. It provides crucial new evidence that swift action to reduce CO2 emissions can prevent biodiversity loss. With mitigation, causing global emissions to peak in 2030 then decline, the proportion of animal species losing half their range would drop from 35% to 20%, and the proportion of plants drops from 57% to 35%. Compared to the baseline scenario of no action whatsoever, biodiversity losses would be reduced by 40%.
With even more stringent mitigation, global emissions would peak in 2016. In fact, climate change would stop increasing by the end of the century. This would result in the proportion of animal species losing half of their range dropping even further to 13%, and of plants dropping to 23%. In this scenario, overall biodiversity loss is reduced by 60%.
The authors state that "the date of peak emissions is arguably more important than the overall amount in terms of reduced impacts and the adaptation time that can be bought." This adaptation time, required for animals and plants (and humans) to adapt to higher temperatures, amounts to 4 decades, but only if stringent and early mitigation keeps global warming to a 2°C rise rather than 4°C (as result of no mitigation) and postpones the impacts of climate change. A delay of the date at which CO2 emissions peak causes reduced effectiveness of mitigation measures to prevent biodiversity loss, so the message is clear: we must act quickly.
Even though the results of this study are ominous, the authors warn that their estimates of biodiversity loss are probably conservative, owing to other effects that climate change brings. These include diseases, extreme weather events, pests, changes in the interactions between species and barriers (natural or unnatural) to dispersal into newly suitable areas.
Most worrying of all is that the our current, increasing rate of emissions is actually greater than in their baseline scenario for this decade, in which taking no action causes range contractions in over half of all plant species and one third of animals. This study issues a stark warning, as Dr Warren concludes: "Our research predicts that climate change will greatly reduce the diversity of even very common species found in most parts of the world. This loss of global-scale biodiversity would significantly impoverish the biosphere and the ecosystem services it provides."
Anna taylor is a freelance conservation journalist, and chief blogger for http://conservation-jobs.co.uk
Image of biodiversity courtesy of www.shutterstock.com
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