**3. Effect of climate change on living organisms**

Changing climate conditions have a profound impact on human health. It can directly affect our health through extreme environmental conditions like drought, heavy rainfall or indirectly through transmissible diseases or malnutrition along with other mental health complications [12]. Severe weather condition helps spread pathogenic microorganisms yielding different waterborne or zoonotic diseases as well as increasing allergens in the air can cause respiratory infections [13, 14]. Climate change is not only impacting human life but also jeopardising wildlife. Many terrestrial and aquatic organisms are at the risk of extinction due to environmental chemical pollutants. Altered environmental conditions can make wildlife more susceptible to chemical toxicants and retard their physiological capability [15]. The impact of climate change on tree mortality is another pressing problem in the forest ecosystem. This temporal rise in tree mortality has been seen in both areas with an increased water shortfall or no such undersupply [16]. Birds, one of the main indicator groups of climate change effects, are more prone to extinction due to severe weather change. It has been predicted that about 900 land bird species will be terminated because of global warming. Moreover, loss of habitat, augmentation of invasive bird species and hunting and spreading of infectious diseases are also contributing factors to bird extinction, which is the outcome of change in climate [17]. Climate change has the most vulnerable effect on agriculture. Changing in climate pattern gives rise to land degradation, desertification or heavy rainfall and floods, which in turn can able to make the soil nutrient deficit, highly saline and less productive. All these stresses are attributable to the risk of global food security [18].

*Climate Change and Algal Communities DOI: http://dx.doi.org/10.5772/intechopen.104710*

The marine ecosystem is greatly affected by climate change. The oceans absorb 90% of the extra heat of the climate, which would be increased to 5–7 times by 2100 if global warming exceeds 2 °C. Additionally, the ocean absorbs up to 30 % of anthropogenic CO2 emissions, which renders acidification in the marine system. Ocean acidification and heat cause depletion of nutrients and O2 supply, which eventually endanger distribution and abundance of marine fishes as well as other organisms, and along with these, climate change also affects demography, calcification and phenology of phytoplankton and zooplankton [19, 20]. It accelerates the bleaching of reef-building corals, which makes great barrier reef (GBR) vulnerable. It has been estimated that a 0.5 °C increase in local temperature may cause rapid degeneration of GBR [21].
