Over a period of time, climatic changes have happened due to nonstop anthropogenic emissions in terms of Green House Gases (GHG) into the ambiance having profound and noticeable regional and global impacts on structure, composition, and functions of natural as well as human-made environments across the board. Climatic changes pose irreversible losses to ecosystems endangering a variety of biodiversity.
According to the Birdlife International, the anthropogenic influences that have brought many faunal and floral photosynthetic rate of many floral species, with a major impact on fast growing plants as compared to the slow growing ones. It reduces nutrient concentrations in plants that accordingly affect animal growth and nutrient requirement. Modification in global nitrogen cycle also affects species composition and productivity, where nitrogen fixation is human induced than by natural process. Dry season affects plant growth as the annual rings being sensitive indicators of the climatic and environmental conditions in which they grow, tend to be closer due to water stress. A number of global climate models foresee increase in species of prime concern to one of the threshold categories of vulnerability, threatening their extinction are not uncommon. A recent UN assessment indicates that an increase in average temperatures between 1.5 & 2.5 degree centigrade would cause extinction of about 20 - 30 percent of plants, animals, insects, besides polar bears whose habitat has largely been threatened.
The Millennium Ecosystem Assessment 2005, highlights that climate change will also have major effect on basic environmental services. Global warming increase will affect agro-ecosystems, rangelands, wetlands, marine and aquatic resources, deserts, coral reefs, and mountain ecosystems besides million of people dependent on these ecological entities for subsistence.
Current global warming phenomenon has accelerated a meltdown of snow and ice reserves causing sea levels go up by about 0.8 millimetres per year affecting millions of people around the world with floods, storms, droughts and losses of coastal wetlands and mangroves as highlighted in the Intergovernmental Panel on Climate Changes (IPCC) Fourth Assessment Report in 2007. Glacial recession in the Himalayas will lead to flooding, avalanches and affect water regimes along with associated floral and faunal species.
Increased concentration of carbon dioxide would enhance extreme high temperature and decrease in extreme low temperature towards the end of the 21st century. This would result in increased duration and frequency of weather spells and dramatic shifts in weather conditions. As a result, varying precipitation and seasonal variability will badly damage vegetation, crops, plants, animals and freshwater supplies over a period of time. Changed climate may favour and facilitate some non-native plants in many parts of the world but their adaptation poses a serious threat to native ecosystems. Moreover, polar bear populations in the Arctic arc under threat. Scientists believe that increase in temperature would affect reproduction and birth rate in terms of sex ratio in some animals. According to BBC, new measurements by US scientists show that since 1996 the Greenland ice sheet has been moving faster during the summer melting season the rate is accelerating as more melted water trickles down from the surface of the sheet to the bedrock.
A brief report of Birdlife International indicates that many species will lose resilience and will be unable to keep up with their changing environmental and climatic scenario. In due course of time, extinctions of species currently considered safe will more likely occur at local and global levels. One recent global study estimated that 15 to 37 per cent of species would face extinction by 2050.