Impact of Climate Change on Biodiversity

 

Climate change is due to the green house effect, the process by which absorption and emission of infrared radiation by gases in the atmosphere warm the earth’s lower atmosphere and surface. Atmospheric gases such as water vapour, CO₂, O₃ and CH₄  act like the glass roof of a greenhouse trapping heat which results in the warming of the planet. That is why it is seen to be analogous to that which occurs within green houses. Man’s actions such as the burning of fossil fuels, farming activities and land use changes have all resulted in an increase in these natural gasses. The earth’s surfaces and lower atmosphere are thus warming rapidly. The phenomenon of ‘Global Warming’ was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896.

The physical aspects of global warming, i.e. how and why it occurs and the climate models that are used to predict future changes in the global climate will be dealt with in detail in the next lesson.  In this lesson we will only focus on the ways in which climate change will impacts global biodiversity.

What will happen when the climate gets warmer?

All ecosystems and species will be exposed to warmer temperature, ice in the polar region will begin to melt and this will result in a rise in sea levels.

There is evidence to suggest that these changes are already taking place. Some of reported facts are as follows:

• Since the mid-1800s, the average global temperature has continuously increased by about 0.6 ^oC   annually.
• During the 20th century the global mean sea level rose by 10cm.
• The volume of glaciers in Switzerland has decreased by 2/3 rds.
• There is a 40% reduction in the thickness of Arctic ice in late summer and early autumn.
• Scientists have revealed that Mount Kenya has lost 92% of its ice while the loss in Mount Kilimanjaro is reported to be 82%.

Effects on Biodiversity

These environmental changes would most definitely have an adverse impact on the different components of biodiversity, i.e on organisms, species and on the ecosystems of which they are apart. Considering the vast array of goods and services that are provided by biota and ecosystems it is inevitable that humans will also be drastically affected by changes in the global climate. We will now look at some of these impacts.

Altering species distributions

Species are sensitive to changes in the climate to different degrees. Those who are highly sensitive would show greater vulnerability. In order to survive climate change such species would have to ‘shift their range’ or in other words move into suitable areas to avoid being adversely affected. For instance species at lower altitudes may be forced to migrate towards higher areas where the temperatures are cooler.

In Canada, some alpine species have been migrating upward 1-4 m per decade. However, it is unlikely that white spruce populations will be able to migrate at a rate matching the pace of climate change.

Many such examples of changes in distribution ranges of species can be found

On the other hand, some species might find the warming of the climate to be beneficial. Species that thrive in warm climates (bacteria, insects etc.) might be able spread into new areas where the climate has now become more favorable than before. Unfortunately many of these species are pests and weeds (we have addressed this issue later on in this lesson). Invasive species will spread their distributions causing havoc in many ecosystems.

Facilitating species extinction

Species extinction may be accelerated due to climate change through alterations in the availability and predictability of food resources, disruption of reproductive cycles and physiology or by increasing the vulnerability / susceptibility of species to parasites and diseases.

Sea ice cover is essential for polar bears and other animals that live in the polar region. The shorter duration of sea-ice cover has been shown to endanger the polar bears in Arctic by allowing les time for feeding. The weight of female polar bears in Canada in 1980 was 650 lbs where as it has reduced to 507 lbs by 2004. Walruses, seals and other marine mammals that rely on sea ice for resting, feeding and breeding are also negatively affected by the melting of ice caps.

Even subtle changes in ambient temperatures have the potential to cause alterations in the physiology of animals and plants. For instance, the ambient temperature determines the sex of baby sea turtles. Research has shown that warmer temperatures increase female.

Changes in the climate have resulted in increased frequency and severity of extreme weather conditions such as floods, hurricanes, drought etc. These in affect breeding patterns of species that are dependent upon specific weather condition.

Flight paths and timing of migration may also change. Migratory species are heavily dependent on wind patterns and ocean currents.