Climate Change

Biodiversity and Climate Change

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Impacts on biodiversity

Climate change is likely to have considerable impacts on most or all ecosystems. The distribution patterns of many species and communities are determined to a large part by climatic parameters, however, the responses to changes in these parameters are rarely simple.

Shifts in distribution of plants and animals

At the simplest level, changing patterns of climate will change the natural distribution limits for species or communities. In the absence of barriers it may be possible for species or communities to migrate in response to changing conditions. Vegetation zones may move towards higher latitudes or higher altitudes following shifts in average temperatures. Movements will be more pronounced at higher latitudes where temperatures are expected to rise more than near the equator. In the mid-latitude regions (45 to 60º), for example, present temperature zones could shift by 150 550 km.

Golden Toad factsheet

Golden Toad Species Data

Barriers to movement

In most cases natural or man-made barriers will impact the natural movement of species or communities. Arctic tundra and alpine meadows may become squeezed by the natural configuration of the landscape, while these and many other natural systems may be further confined by human land-use patterns. Many national parks and protected areas are now surrounded by urban and agricultural landscapes which will prevent the simple migration of species beyond their boundaries.

Changing patterns of precipitation and evaporation

Rainfall and drought will also be of critical importance. Extreme flooding will have implications for large areas, especially riverine and valley ecosystems. Increasing drought and desertification may occur in tropical and sub-tropical zones, and at least one model has predicted a drying out of large parts of the Amazon.

Rapid changes

Rates of change will also be important, and these will vary at regional and even local levels. The maximum rates of spread for some sedentary species, including large tree-species may be slower than the predicted rates of change in climatic conditions.

Species interaction

In many cases further complications will arise from the complexity of species interactions and differential sensitivities to changing conditions between species. Certain species may rapidly adapt to new conditions and may act in competition with others.

Shifting seasons

Changes in seasons are already being noticed in many temperate regions. Birdsong is being reported earlier and spring flowers are emerging when it was once winter. In agricultural landscapes changes in the length of growing seasons may improve productivity in mid-latitudes and increase the potential for arable crops at high latitudes. Negative impacts may include increased ranges of insect pests and diseases, and failure of crops in some regions from drought or flooding.

The coastal margins

On the relatively narrow habitats of the coastal margins, especially where these are backed by areas of intense human use, rising sea levels may lead to the squeezing out of important coastal habitats.

Warmer oceans

Rising sea temperatures will further affect the distribution and survival of particular marine resources. Corals have already shown an extremely high sensitivity to minor increases in temperature, while other studies have shown dramatic changes in the distribution and survival of the Pacific salmon in the late 1990s.

Chemical effects

In addition to causing a warming effect, increased concentrations of atmospheric carbon dioxide are known increase rates of photosynthesis in many plants, as well as improving water use efficiency. In this way the climate changes may increase growth rates in some natural and agricultural communities.

Sensitive ecosystems

Biome, ecosystem. Landscape type	Key climatic variables	Implications for biodiversity
Wetlands	Mean summer temperature Mean annual precipitation Flooding	Increased variability in the hydrological cycle leaving inland wetlands to dry out with lower species diversity Warming of 3 - 4°C. could eliminate 85% of all remaining wetlands
Coastal marshes	Relative rate of sea-level rise, changes in hydrological balance Storm frequency and severity	Habitat loss of estuaries and deltas, particularly where these are backed by agricultural or urban land, preventing natural retreat Implications on migratory species and their flyway patterns
Forests (general)	Changes in rainfall, temperature and potential evapotranspiration. Increased frequency of fire and storms.	Major changes in vegetation types, forests may disappear in certain areas at a rate faster then the potential rate of mirgration to, or re-growth in, new areas
Tropical Montane Forest	Changes in degree of cloud cover versus and sunlight hours Hurricane frequency and severity Drought frequency and annual rainfall distribution	Drying out and invasion or replacement of montane species by lower montane or non-montane species
Tropical Montane Forest Initiative
Boreal Forest	Mean annual temperature Fire frequency and severity Storm frequency and severity Growing season length Increases in pest attack	Significant losses in some areas, mainly through fires and pest attack. Expansion of boreal forest into Arctic areas
Boreal Forest Project
Arctic habitats	Mean annual temperature Season length Precipitation	Vegetation changes with vast losses of tundra and forest extension Thawing of permafrost leading to additional release of soil carbon as CO₂ in a positive feedback loop
Alpine / Mountains	Mean annual temperature Snow fall and melt Growing season length	Altitudinal migration of habitats, with invasion of alpine meadows by forest systems, highest altitude habitats may be unable to migrate
Mountains and Forests Project
Low-lying islands	Relative sea-level rise Storm frequency and severity	Loss of land area, seabird nesting colonies. Increased human demands on remaining terrestrial habitats
Arid and semi-arid areas	Precipitation patterns Minimum winter temperatures	With a few exceptions deserts are expected to become hotter and drier Desertification into sub-Saharan Africa and Central Asian Steppes Salinisation Loss of grassland Loss of arable land
Coral Reefs	Sea-surface temperature, indirect chemical effects of higher CO2 concentrations in the water	Prolonged exposure to even minor (>1ºC) rises in temperature causes coral bleaching and may result in coral death Impacts may be compounded by chemical effects of increasing CO2 concentrations which could reduce calcification rates (skeletal development, growth rate).
Mangroves	Relative rate of sea-level rise, changes in hydrological balance in estuarine systems Storm frequency and severity	Decrease in extent as coastal zone becomes "squeezed" between sea and inland agriculture

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