Biodiversity under pressure from climate change

Climate change poses yet another threat to the world's biodiversity which is already under great stress from humankind's activities. But the fact that biodiversity itself can contribute to mitigating the effects of human-induced climate change serves to underscore the importance of protecting and restoring ecosystems.

Chee Yoke Heong

Issue No. 231/232 (Nov/Dec 2009)

BIODIVERSITY is the variability among living organisms and their habitats, including the diversity within species, between species and of ecosystems. Biodiversity is essential for human survival because it provides goods and services, such as food, fuel and energy, medicines, clean water and air, flood/storm control, soil stabilisation, pest and disease control, and supports livelihoods and cultural and spiritual values.

However, this biodiversity is already under threat from increased demand for resources, land degradation (e.g. desertification), the loss of habitats, pollution, invasive non-native species as well as genetically modified organisms. Climate change constitutes an additional challenge as it often exacerbates the impacts of these other stresses.

Human-induced climatic changes and greenhouse gas emissions into the atmosphere are already having observable impacts on ecosystems and species. While some ecosystems and species have shown a capacity for natural adaptation, others have exhibited negative impacts which threaten biodiversity. One of the major risks is the increased rate of species extinction, with negative consequences for the services that these species and ecosystems provide. The latest Intergovernmental Panel on Climate Change (IPCC) report of 2007 estimated that 'approximately 20 to 30% of plant and animal species are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5øC.' At the current observed temperature rise, an estimated 6-8% of the species may be extinct.

'For increases in global average temperature exceeding 1.5 to 2.5øC and in concomitant atmospheric CO2  [carbon dioxide] concentrations, there are projected to be major changes in ecosystem structure and function, species' ecological interactions and shifts in species' geographical ranges, with predominantly negative consequences for biodiversity and ecosystem goods and services, e.g. water and food supply,' it adds.

However, a more recent 2008 study by US National Aeronautics and Space Administration (NASA) scientist Jim Hansen and his team shows that the IPCC is actually too conservative and that CO2 has twice the effect on temperature than the IPCC attributed. This has led to the conclusion that the CO2 concentration target to aim for is 350 parts per million (ppm), and not 450 ppm as indicated by the IPCC.  The head of the IPCC RK Pachauri has agreed with the new target. Hansen's work warns of even more intense impacts.

Ecological and economic costs

The negative impacts of climate change on biodiversity have significant ecological and economic costs.

 On the global scale, ecosystems are currently acting as carbon sinks, storing about 30% of human-generated emissions annually that will slowly be released into the atmosphere if no action is taken. The conversion from sink to source is evidenced, for example, in the increase in soil respiration, regional decreases in precipitation or increases in seasonality, thawing of permafrost and deterioration in peatlands and increases in frequency of wildfires. It has been suggested that this feedback could increase carbon concentration, leading to a rise in temperatures of 0.1-1.5øC by 2100.

The wild relatives of crop plants which are important sources of genetic diversity for crop improvement but the use of which is not well known, are threatened by climate change. For example, a plant called 'shungu panga' that grows close to the wetlands is used by the indigenous communities in the Amazon for medicinal purposes but is fast disappearing as the wetlands are affected by climate change.

 The projected impacts of climate change on coral reefs and other commercially important marine and freshwater species will have serious implications for fisheries and the livelihoods of coastal communities. It is estimated that climate change and the absence of strong mitigation efforts could result in the loss of up to 88% of the coral reefs in South-East Asia over the next 30 years. In addition, ocean acidification may cause pH to decrease over the next decades, causing severe death of shellfish and reef-building corals, thus affecting fishery production and ecotourism, and leading to potentially major ecological impacts, according to a report by the UN Convention on Biological Diversity.

Biodiversity loss and degradation of ecosystems resulting from climate change have a greater impact on the poor. Many areas which are rich in biodiversity are located in the developing world where millions of people rely directly on the natural environment to meet their basic needs. They are therefore more vulnerable to biodiversity-related impacts of changes such as temperature and sea-level rise, changes to ocean currents and extreme weather events.

 Among the vulnerable groups, indigenous peoples will be disproportionately impacted because their livelihoods and cultural and religious ways of life are intimately linked to their environments. Their livelihoods will be adversely affected if climate and land-use change lead to losses in biodiversity, including losses to habitats of animals which are important food sources. 

 A few studies have attempted to quantify the lost value associated with the impacts of climate change specifically on biodiversity. The Economics of Ecosystems and Biodiversity report, commissioned by the G8, estimates the loss of biodiversity worldwide to be worth 7% of world GDP in 2050. Another study puts the lost value for protected areas associated with the projected impacts of climate change in Africa at $74.5 million by 2100. Meanwhile, the World Bank estimated that coral reef degradation in Fiji attributable to climate change is expected to cost between $5 million and $14 million a year by 2050 due to losses from fisheries, tourism and habitat.

Regional impacts

The IPCC predicts the probability of higher temperatures, more heatwaves, heavy/reduced rainfall, droughts and other extreme weather throughout this century. Since biodiversity underlies many of the goods and services on which humans depend, climate change will have a profound impact in many regions of the world.

 In Africa, many thousands of plants are affected by a shift in rainfall seasonally, with the montane areas particularly threatened by increases in temperature. Major rivers which are highly sensitive to climate variation will see average runoff and water availability decrease. This will affect biodiversity such as a decrease in some freshwater fish; a reduced runoff could lead to a reduction in the wetland areas which are among some of the most important in the world. The possibility of an increase in infectious diseases and insect pests could lead to an increase in agricultural and forestry losses with unknown consequences to many ecosystems. Less rainfall could exacerbate desertification especially in southern, north and west Africa. On top of these, there is a risk of losses of plants and animals that have limited mobility in areas where rainfall may change seasonally, or where tree/grass balance is sensitive to CO2 conditions and other climatic factors.

As for Asia, a sea-level rise could cause large-scale inundation of freshwater wetlands along the coastline, such as in China, and reduction in or loss of flat coastal habitats; mangroves (e.g. those in the Sundarbans) and coral reefs which support a diversity of wildlife such as tigers, otters, deer, crocodiles, crabs and marine turtle species are at great risk from sea-level rise. With rising sea waters, these mangroves and the many resident species will be wiped out, adversely affecting local human populations. With climate change, the frequency and intensity of forest fires and pest outbreaks in the boreal forest are likely to increase. These forests are also expected to be affected by floods and increased volume of runoffs from the melting permafrost. Rising temperatures and decreases in precipitation could also lead to deterioration of water quality.

With regard to Latin America, the rate of biodiversity loss is expected to accelerate as a result of climate change. Mangrove ecosystems will be degraded or lost by rising sea levels, leading to a decline in some fish species. There will also be adverse impacts on cloud forests, tropical seasonally dry forests and shrublands, low-lying habitats (coral reefs and mangroves) and inland wetlands. The loss and retreat of glaciers would adversely impact runoff and water supply in areas where glacier melt is an important water source, thus affecting water systems that are rich in biodiversity. In addition, climate change will bring disruption to the lives of mountain peoples by altering the already marginal food production and the availability of water resources and habitats of many species that are important to indigenous peoples.

The small island states which are most vulnerable to rising sea levels are likely to experience the loss of many reef-associated communities and species due to the bleaching and the reduced development rate of their coral reefs. Consequently, loss of revenues from key sectors such as tourism and fisheries could be expected.  Mangroves, seagrass beds, other coastal ecosystems, and the associated biodiversity would be adversely affected by rising temperatures and accelerated sea-level rise, while saltwater intrusion into freshwater habitats will occur.

Inundation and flooding of low-lying forested areas in islands will lead to the loss of some endemic bird species, as the majority of threatened bird species are found in forested habitats.

Some observed effects

Already, ecosystems and species are feeling the heat from human-induced changes in the climate and atmospheric CO2. For instance, some species are moving further to higher latitudes and elevations. These are mostly recorded in temperate zones where long-term data records are available. Though data are scarce for tropical regions, biodiversity losses have already been recorded in some areas.

Extreme temperatures or precipitation which may be exacerbated by climate change will be more damaging to biodiversity than gradual climatic change. Extreme temperatures exceeding the tolerance limits of species have caused mortality in Australian flying-fox species and other species. As another example, floods have caused catastrophic mortality in desert rodents, leading to changes in population levels. 

While the implications of climate change on biodiversity need to be recognised, so too should the role of biodiversity in mitigating the effects of human-induced climatic changes. Conserving natural land and marine environments and restoring degraded ecosystems can contribute to international efforts to mitigate climate change, preserve biodiversity and livelihoods, and arrest desertification.

Well-functioning ecosystems underpinned by biodiversity are essential because of their role in the global carbon cycle and carbon storage. Forests and soil are major carbon storage facilities on land and hence continued deforestation and degradation at current rates need to be halted. There should also be a stop to the clearing of wetlands and peat lands which contain a significant portion of carbon stored in soil.

Crop diversity also provides a natural insurance against major ecosystem changes, be it in the wild or in agriculture, and plays a major part in ensuring food security. It is now predicted that genetic diversity will be most crucial in highly variable environments and those under rapid human-induced climate change. The larger the number of different species or varieties present in one field or in an ecosystem, the greater the probability that at least some of them can cope with changing conditions. Species diversity also reduces the probability of pests and diseases.

Protecting and restoring ecosystems can even be a cost-effective and affordable long-term means to help human communities defend against the effects of climate change. For instance, instead of building infrastructure such as seawalls and levees to protect against storm surges or high winds due to more intense cyclones, which can be expensive and need ongoing maintenance, efforts can be channelled towards the protection and restoration of 'green infrastructure' such as healthy coastal wetlands (including mangrove forests) and coral reefs, which require less maintenance and provide additional benefits to the communities in terms of food, raw materials and livelihoods as well as promoting biodiversity.

The experience of Vietnam is a case in point. The Vietnamese Red Cross began planting mangroves in 1994. By 2002, 12,000 hectares had cost $1.1 million, but saved annual levee maintenance costs of $7.3 million, shielded inland areas from typhoon Wukong in 2000 and restored livelihoods in planting and harvesting shellfish.

Impacts on biodiversity of climate change 'solutions'

Meanwhile, there is a wide range of climate change mitigation activities which can displace fossil fuel energy, thus reducing greenhouse gas emissions, but they need to be evaluated closely as these have potential implications for biodiversity and ecosystem services. 

While bioenergy can contribute to energy security, rural development and mitigating climate change, there are concerns that some first-generation agrofuels are accelerating deforestation with adverse effects on biodiversity, and, if a full-cycle analysis is taken into account, may not actually reduce greenhouse gas emissions.

The long-term stability of biochar in soils is, as yet, unknown and its large-scale development could result in additional land-use pressures. Hydropower is widely adopted by developing countries as a substitute to fossil fuel but large-scale hydropower systems, in particular, have been shown to be detrimental to biodiversity and can have adverse social effects.

A range of geo-engineering techniques has been proposed but their potential and implications for biodiversity are not well understood. Experiments in injecting additional iron to nutrient-rich but iron-poor regions of the ocean have produced phytoplankton blooms and increased the ocean uptake of CO2 into surface waters for a week. But the consequences of larger, longer-term introductions of iron remain uncertain. Many concerns, all of which are likely to affect biological diversity negatively, are still not resolved.              

Chee Yoke Heong is a researcher with the Third World Network.

References

Cotter J. and Tirado R. 2008. Food Security and Climate Change: The answer is biodiversity: A review of scientific publications on climate change adaptation in agriculture. Greenpeace.

Hansen J, Sato M, Kharecha P, Beerling

D, Berner R, Masson-Delmotte V, Pagani M, Raymo M, Royer DL and Zachos JC. 2008. Target atmospheric CO2: where should humanity aim?  http://arxiv.org/ftp/arxiv/papers/0804/0804.1126.pdf <http://arxiv.org/ftp/arxiv/papers/0804/0804.1126.pdf>

IPCC. 2002. Technical Report V. Climate Change and Biodiversity.

IPCC. 2007. Climate Change 2007: Synthesis Report.

Secretariat of the Convention on Biological Diversity. 2009. Connecting Biodiversity and Climate Change Mitigation and Adaptation: Report of the Second Expert Group on Biodiversity and Climate Change, SCBD. (CBD Technical Series no. 41).

*Third World Resurgence No. 231/232, November-December 2009, pp 33-35