Essay on the Impact of Climate Change on Biodiversity | Geography

Biodiversity in all its components (e.g. genes, species, ecosystems) increases resilience to changing environmental conditions and stresses. Climate change could affect a number of physical and biological processes in which the health and composition of terrestrial ecosystems depend. Genetically diverse populations and species-rich ecosystems have greater potential to adapt to climate change. Leemans and Eickhout (2004) showed that 1°C warming alters more than 10 per cent of all ecosystems.

At 2°C and 3°C rise, 16 per cent and22 per cent of all terrestrial ecosystems can change significantly. IPCC report lists the species which will be under threat as a result of climate change and global warming which includes the mountain gorilla in Africa, amphibians that only live in the cloud forests of the neo-tropics, forest birds of Tanzania, Bengal tiger and other species in the Sundarban wetlands, rainfall sensitive plants found only in the Cape Floral Kingdom of South Africa, polar bears, penguins etc.

Coral reefs, mangroves, coastal wetlands, mountain ecosystems found in the upper 200-300 meters of mountainous areas, prairie wetlands, and permafrost ecosystems are some of the natural habitats which are threatened due to global warming (IPCC, 2007). These species or ecosystems are unable to migrate in response to climate change because of their particular geographical locations. Several studies revealed that due to increased temperature in recent decades, certain species began breeding and migrating earlier than expected.

Other studies found that the geographical range of numerous species had shifted pole ward or moved to a higher elevation – indicating that some plants and animals are occupying areas that were previously too cold for survival. They conclude that a rapid temperature rise in combination with other environmental pressures “could easily disrupt the connectedness among species” and possibly lead to numerous extinctions.

Malcolm et al. (2006) assessed the potential effects of climate change on terrestrial biodiversity on a global scale, rather than considering only individual species. They reported that doubling of present CO₂ concentration and resulting temperature rises could potentially eliminate 56,000 plant and 3,700 endemic vertebrate species in the 25 hotspot regions.

Areas particularly vulnerable to climate change include the Cape Floristic region of South Africa, Caribbean regions, Indo-Burma, the Mediterranean Basin, southwest Australia, and the tropical Andes as the species in these regions have restricted migration options due to geographical limitations.

If climatic conditions shift quickly enough, slower moving species may be left behind, especially when human activities have destroyed and fragmented existing habitat. Due to climate change, habitats can be shifted, and eventually habitats can be lost from many areas. However, species with short generation time, such as microbes and insects, may adapt more successfully to climate change than those species with long generation time.

Here are some examples of habitat loss, change in productivity and species extinction in response to climate change and global warming as revealed recently:

i. A vast region of Amazon Rain Forest, which holds a high proportion of global biodiversity, is on the brink of being turned into desert, with catastrophic consequences for the world’s climate. The forest can’t withstand more than two consecutive years of drought without breaking down.

ii. Crop productivity is projected to increase slightly at mid to high latitudes for local mean temperature increase of up to 1-3°C depending on the crop, and then decrease beyond that in some regions. At lower latitudes, especially seasonally dry and tropical regions, crop productivity is projected to decrease for even small local temperature increases (1-2°C), which would increase the risk of hunger.

The poorest countries would suffer most, with reductions in crop yields in most tropical and sub-tropical regions due to decreased water availability and new or changed insect pest incidence. In Africa and Latin America many rain fed crops are near their maximum temperature tolerance, so that yields are likely to fall sharply for even small climate changes; falls in agricultural productivity of up to 30 per cent over the 21^st century are projected.

Production of rice, maize and wheat in the past few decades has declined in many parts of Asia due to water shortage, increasing frequency of El Nino and reduction in the number of rainy days. All of these factors are related with climate change (IPCC, 2007). In a study at the International Rice Research Institute, the yield of rice was observed to decrease by 10 per cent for every 1°C increase in growing-season minimum temperature.

The climatic change could affect agriculture in several ways:

a. Productivity, in terms of quantity and quality of crops.

b. Agricultural practices, through changes of irrigation conditions and agricultural inputs such as herbicides, insecticides and fertilizers.

c. Environmental effects, i.e., frequency and intensity of soil drainage (leading to nitrogen leaching), soil erosion and reduction of crop diversity.

d. Rural space, through the loss and gain of cultivated lands, land speculation, land renunciation, and hydraulic amenities.

e. Adaptation, i.e., organisms may become more or less competitive, as well as humans may develop urgency to develop more competitive organisms, such as flood resistant or salt resistant varieties of rice.

iii. Due to global warming, spring arrives earlier in Europe as a result of which birds are being forced to change their migration patterns. They arrive in northern Europe earlier in time for the start of spring. The familiar bird species of Britain will be driven hundreds of miles further north by the end of the century.

iv. Amphibian populations are declining due to global warming in the designated wilderness areas and national parks. Pounds et al. (2006) reported that global climate change has made conditions more favorable for a new disease (chytridiomycosis), thus indirectly leading to extinctions and declines of amphibians. Because of the permeable skin, biphasic lifestyles and unshelled eggs, amphibians are extremely sensitive to small changes in temperature and moisture.

Amphibians in temperate regions may be even more susceptible to increased temperature. In eastern Australia, Ingram (1990) found a correlation between draught and massive declines of stream-dwelling rain forest amphibians. Local changes in the environment can also decrease immune function of the amphibians and lead to pathogen outbreaks and elevated mortality. Gervasi and Foufopoulos (2007) found that amphibian immune responses become increasingly weaker and leukocyte counts were increasingly lower with higher desiccation.

v. Due to the loss of sea ice habitat, polar bear is under threat. Stirling et al. (1999) observed that due to loss of ice sheets, Hudson Bay polar bears are coming ashore for several months of fasting in progressively poorer condition. Hudson Bay polar bears prey primarily on ringed seals (Phocahispida), the population of which is in decline due to a loss of these stable ice flows. Due to nutrient deficiency, polar bears will use stored fat as an energy source, which can remobilize the Persistent Organic Pollutants stored in their tissues and potentially resulting in the dual stresses of starvation and chemical toxicity.

vi. The pH is an important water quality indicator as fishes and other organisms are sensitive to pH. Ocean surface pH has already decreased by 0.1 pH units in colder waters and almost 0.09 pH units in warmer waters. If atmospheric CO₂ concentrations continue to increase, another 0.3 pH unit decrease of oceanic surface waters may occur. Furthermore, as temperature increases, an increased proportion of the water molecules dissociate to H⁺ and OH^–, decreasing water pH, which will affect the ocean biodiversity.

vii. Extreme environmental conditions, such as elevated water temperature, low dissolved oxygen or salinity and pH, can have deleterious effects on fishes. Suboptimal environmental conditions can decrease foraging, growth, and fecundity, alters metamorphosis, and affects endocrine homeostasis and migratory behavior. The progressive acidification of oceans is expected to have negative impacts on marine shell-forming organisms (e.g., corals) and their dependent species.

viii. Corals are vulnerable to thermal stress and have low adaptive capacity. Increases in sea surface temperature of about 1-3°C are projected to result in more frequent coral bleaching events and widespread mortality, unless there is thermal adaptation or acclimatization by corals. Most of the pigmentation within corals is within the symbiotic algal cells-the zooxanthellae. Corals losing their zooxanthellae cause coral bleaching.

Thermal bleaching occurs when the coral is exposed to prolong above- normal (or below-normal) temperatures, resulting in additional energy demands on the coral, depleted reserves, and reduced biomass. Bleaching causes a decrease in the growth rate of corals, and the time taken for a coral to recover from a bleaching event may be several years or decades. If the frequency of bleaching increases, then the capacity for coral reefs to recover is diminished.

ix. Due to warm habitats, in polar regions there is a possible shift in spawning times, alteration of bioenergetics and changes in transport of larvae in the populations of north sea cod, haddock, herring, and sardines. In temperate regions, the distribution of pacific salmons (Oncorhynchus sp.) shifts northwards, their population decreases and the size is also changed.

x. The bioavailability and toxicity of Persistent Organic Pollutants and pesticides in wildlife may increase in response to rising temperatures and salinity. An underlying mechanism of this toxicity is that temperature can alter the toxic-o-kinetics of chemical pollutants in organisms; or the increasing temperature can alter homeostasis and other key physiological mechanisms, thereby can magnify the adverse effects of contaminants.

xi. Species that are especially sensitive to climate change may be used as indicator species (‘bio-indicators’) for assessing the climate sensitivity of whole ecosystems. A number of herbaceous plant species, butterflies and birds are identified as suitable bio-indicators for climate change. Natural eco-climatic transitions or eco-tones may be especially suitable for monitoring effects of climate change, because they are likely to be especially sensitive to climate change.