Friday, December 01, 2006

Climate change & species extinctions

A severe environmental consequence of climate change is likely to be an ensuing wave of species extinctions and the consequent destruction of biodiversity value.

Plants and animals face difficulties in migrating away from changed climatic conditions, even with gradual global warming, because of human fragmentation of vulnerable ecosystems. If the change is abrupt – for example over a period of around 50-100 years – then effects will be much more severe. In Australia the Climate Change Network identify at least 90 Australian species at risk from climate change.

Consider for example:

1. A species such as the Mountain pigmy possum which lives in the Australian Alps. This exists in a narrow ‘temperature envelope’ - Brereton et al. (1995) show it disappears with an increased temperature of 1 degree C.

2. A habitat such as Southwest Western Australia (Australia’s key biological ‘hotspot’) which accommodates many of the 92 unique Dryandra plant species. These could again be seriously threatened by a temperature rise of as little as 1 degree C. See Pouliquen-Young and Newman (2000). The best of the Australian banksias is endemic to this region (B. coccinea) – my favourite Australian wildflower!

At the global level there are still more pessimistic forecasts. Thomas et al. in a letter to Nature (and here) forecast that between 13-37% of all species will be wiped out by climate change by 2050 without comprehensive measures to address global warming. A comprehensive review, by Camille Parmesan, of relevant scientific literature reaches similar conclusions (here).

I recently came across a 2004 report from the Australian Department of Environment and Heritage which addresses biodiversity conservation concerns for Australia from the perspective of designing policies that will ameliorate the effects of climate change. The presumption is the very reasonable one that climate change is already occurring. The objective is to devise an ‘action plan’ for addressing it. This action plan will:

  • Identify research areas to better understand impacts.
  • Adapt existing conservation strategies.
  • Improve communication between researchers and biodiversity managers.
  • Increase community awareness of the issues.

The policy mix includes reducing climate change impacts, promoting natural adaptation to change by facilitating ecological connectivity to aid migration and dispersal of species, protecting refugees and creating specific management zones around important habitats. A 3-year plan was proposed for 2004-2007 with a revised plan to be drawn up in 2007.

What is our climatic future? Most of Australia will warm from 1-6 degrees C over the next 100 years with annual rainfall likely to fall in the south and east – where evaporation will also increase. Some eastern and coastal areas will have moister summers. Extreme rainfall and tropical cyclones could become more intense. A detailed picture is here.

The implication for certain species is severe since many can survive only in limited climatic ranges and will be threatened if they cannot migrate because of clearing or environmental differences.

Areas of concern include the Australian Alps, the wet tropics, the coral reefs, arid and semi-arid habitats, freshwater wetlands and riverine environments. See Howden et al (2003) and Hughes (2003).

The effects of climate change will include a reduction in the geographic range of many species, changes to their reproductive lifecycles, changes in their population dynamics and survival with higher extinction probabilities for species already threatened. Many species will seek to move either south or towards higher elevations. There will also be increased pressure from invasive species such as weeds and pest species as native communities are exposed to stress. There will also be increased fire risks. Finally, there will be specific problems for coastal and estuarine habitats (mangroves, coastal wetlands, seagrass) due to rising sea levels.

Many components of the program involve conservation biology – improve capacities to respond to climate change, minimising climate impacts on key terrestrial and marine ecosystems, minimising invasive species impacts and so on.

But a crucial objective of the action plan is to improve understanding of climate change impacts and here there is a key role for economics is to identify the potential economic costs and benefits of climate change impacts on biodiversity, ecosystem processes, functions and services. This includes undertaking social cost/benefit analyses of possible biodiversity adaptation processes including doing nothing – tasks that were to be initiated in 2006.

There is also the task of incorporating climate change impacts into natural resource and land-use planning and the rationale for this is primarily economic. Adapting existing programs is likely to be the most cost effective way of dealing with climate change since these programs already have infrastructure and are in place. These existing programs can be undermined by climate change – for example through the increasing spread of invasive species. Thus a review of existing programs is called for particularly with respect to the conservation of protected areas.

The economic questions that occur to me are:

1. What is the assumption about the policy response to global warming.

2. If we take a pessimistic assessment of the likely success of climate change measures what insurance policies can be adopt to prevent extinctions. The report simply assumes that captive breeding and other strategies will be relatively expensive compared to adapting current conservation policies. They may however make sense as insurance options.

3. How can the national reserve systems be linked to provide corridors for species migrations in the face of warming? How can such measures be linked to agricultural land reclamation programs? What are the cost and benefit implications of such programs?

4. What, if anything, are the twists to species conservation economics that are posed by climate change issues?


R. Brereton, S. Bennett & I. Mansergh, ‘Enhanced Greenhouse Climate Change and its Potential Effect on Selected Fauna of South-Eastern Australia: A Trend Analysis’, Biological Conservation, 72, 1995, 39-354.

L. Hughes, Climate Change in Australia: Trends, Projections and Impacts, Australian Ecology, 28, 2003, 423-443.

O. Pouliquen-Young & P. Newman, The Implications of Climate Change for Land-Based Nature Conservation Strategies, Final Report 96/1306. Australian Greenhouse Office, 2000.

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