Article:

Warren, R., Price, J., Fischlin, A., Midgley, G., 
   & Santiago de la Nava, S., 2010.  Increasing impacts 
   of climate change upon ecosystems with increasing 
   global mean temperature rise.  Clim. Change, 98 
   (publ.  online 21.Aug.): 1-37. doi: 10.1007/s10584-010-9923-5

Abstract:

It is shown that the current literature projects a dramatic and substantive increase of climate change impacts upon ecosystems with annual global mean temperature rise (ΔTg), with these impacts increasing sharply, especially in biodiversity hotspots of the world, at temperatures close to 2°C above the pre-industrial level. This is demonstrated through a search and subsequent integration of peer-reviewed studies which provide quantified estimates of ecosystem changes related to quantified local or global scale climate changes. The integration allows all studies to be referenced to a common pre-industrial base-line for temperature, employing up-scaling techniques where necessary, and combined into a single table. This details how impacts have been projected on every continent, in the oceans, and for the globe as a whole, for a wide range of taxa. Currently, plants and animals are already responding to climate change, for example through changes in range and phenology; coral reefs have already experienced severe bleaching events and the ocean surface waters have already become acidified by 0.1 pH units. As temperatures continue to rise the literature projects range losses and extinctions in a number or locations, with coral reefs bleaching with greater frequency. Impacts are then projected to increase sharply and by implication rapidly around the world as temperatures approach ΔTg = 2°C with a sharp rise in projected extinction risks in Australia, Europe, South America and Africa; with keystone species at risk in the Southern Ocean; a risk of saturation of the sink service of the terrestrial biosphere and major losses of the Amazon rainforest; and losses of key local ecosystems such as the African Great Lakes wetlands. Beyond 2°C above pre-industrial levels high extinction risks (several tens of per cent of endemics) are projected, particularly in biodiversity hotspots which contain most of the world’s species, and these impacts increase markedly as temperatures continue to increase. This provides some justification for the limit which the EU has suggested is appropriate for annual global mean temperature rise, which is also 2°C above the pre-industrial, since Article 2 of the UNFCCC states that climate policy should be set such that ecosystems can adapt naturally. However, it seems unlikely that major changes in ecosystems such as species extinctions will be completely avoided even if the 2°C limit is not breached. Since impacts on ecosystems are also dependent on rates of change and transient temperatures experienced between the present day and the time when equilibrium temperature is reached, the rate of temperature increase should also be minimised. The threat to biodiversity from climate change increases the need to protect existing ecosystems from land use change policies. Avoided deforestation is a win-win scenario for protecting ecosystems from future climate change, since it also reduces emissions of greenhouse gases to the atmosphere.

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