Dr. M Abul Kashem Mozumder and Dr. Md. Shairul Mashreque :
Biodiversity encompasses the variety of living beings on earth. In short, in other words it means variation of life. Microorganism, plants, animals and ecosystems such as coral reefs, forests, rainforests, deserts etc. all constitute what we call bio-diversity. Bio-diversity is also the total variety of life on earth. The air we breathe, the water we drink and the food we eat all rely on biodiversity. In fact it includes all flora and fauna of nature.
The United Nations Environment Programme (UNEP) stated:" biodiversity typically measures variation at the genetic, the species, and the ecosystem level. Terrestrial biodiversity tends to be greater near the equator which seems to be the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth, and is richest in the tropics. These tropical forest ecosystems cover less than 10 percent of earth's surface, and contain about 90 percent of the world's species. Marine biodiversity tends to be highest along coasts in the Western Pacific, where sea surface temperature is highest, and in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, but will be likely to slow in the future. he period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity. Named the Holocene extinction, the reduction is caused primarily by human impacts, particularly habitat destruction Conversely, biodiversity positively impacts human health in a number of ways."
At least 40 per cent of the world's economy and 80 per cent of the needs of the poor depend on diverse natural resources. 'The richer the diversity of life, the greater the opportunity for medical discoveries, economic development, and adaptive responses to such new challenges as climate change.'
A research study stated that healthy biodiversity provides a number of natural services for everyone:
· Ecosystem services, such as
n Protection of water resources
n Soils formation and protection
n Nutrient storage and recycling
n Pollution breakdown and absorption
n Contribution to climate stability
n Maintenance of ecosystems
n Recovery from unpredictable events
· Biological resources, such as
n Medicinal resources and pharmaceutical drugs
n Wood products
n Ornamental plants
n Breeding stocks, population reservoirs
n Future resources
n Diversity in genes, species and ecosystems
· Social benefits, such as
n Research, education and monitoring
n Recreation and tourism
n Cultural values
Climate change has been reported in the distribution of species. In general, many species have expanded their ranges 'poleward in latitude and upward in elevation.' According an expert report, "Evidence of contraction in species' distribution is limited, however, possibly due to reporting difficulties and time lag in such contractions due to a wide variety of possible mechanism such as population dynamics. Populations of many species have declined, and although in some cases climate change is believed to have contributed to the decline, attributing this is fraught with difficulty as it is likely to be only one driver amongst many. At the species level, changes observed that can be attributed to climate change involve those surrounding phenology (the timing of events). Many birds and insects are showing changes, such as earlier onset of migration, egg-laying and breeding. In terms of ecosystems, there has been some evidence on changes in distribution e.g. desert ecosystems have expanded, and tree lines in mountain systems have changed. Changes in the composition of ecosystems have also been observed (e.g. increased lianas in tropical forest). Such changes may affect ecosystem function and the ecosystem services they provide. Changes in biodiversity and ecosystem services due to climate change are not all negative, with some species either thriving or adapting. Most of these observed changes are modest, which is possibly due to the limited change in climate that has occurred. However, future projected changes in climate are much larger. IPCC AR4 suggests that approximately 10% of species assessed so far will be at an increasingly high risk of extinction for every 1°C rise in global mean temperature, within the range of future scenarios modeled in impacts assessments (typically <5°C global temperature rise). Aquatic freshwater habitats and wetlands, mangroves, coral reefs, arctic and alpine ecosystems, and cloud forests are particularly vulnerable to the impacts of climate change. Montane species and endemic species have been identified as being particularly vulnerable because of narrow geographic and climatic ranges, limited dispersal opportunities, and the degree of non-climate pressures. Potential impacts of climate change on genetic diversity are little understood, though it is thought that genetic diversity will increase the resilience of species to climate change. Modeling studies on the potential impact of climate change on species indicates pole ward shifts and changes in altitude, range expansions or contractions corroborating the current evidence in the most part. However, such studies highlight the individualistic nature of species' responses to climate change, which is likely to have a large impact on future composition of ecosystems. Structure of ecosystems may also change. Models suggest this may have an impact on ecosystem function. For example, modeling suggests increases in net primary production in northern Europe but decreases in areas where water is a limiting resource. Changes in productivity are likely to change services such as nutrient cycling due to changes in litter fall. Other potential changes to ecosystem services due to climate change, include changes to the provisioning services (e.g. food, fibre, timber), carbon storage and sequestration, water regulation and disease regulation. Changes to ecosystems as a result of climate change are likely to have significant and often negative social, cultural and economic consequences. However, there is still uncertainty about the extent and speed at which climate change will impact biodiversity and ecosystem services, and the thresholds of climate change above which ecosystems are irreversibly changed and no longer function in their current form. Tipping points are points at which a system passes from one steady state to another. These are used for either climate tipping points or ecosystem tipping points. An example of the latter is Amazon forest dieback."
Several methods and tools have been used to assess the impact of climate change on biodiversity. Bio-diversity has long seriously been affected by anthropogenic climate change. Climate change has become a formidable threat to bio-diversity. This is because the developers exploit the nature in the manner that ultimately impairs ecological balance. The developers through the use of science and technology try to construct road infrastructures, power plants, modern residential enclaves, industries etc. that may sometimes directly go against nature. The scientists and technocrats being developers use oil, gases and other fossil fuel that give rise to a number of contraindications fetching a lot to bring about environment degradation. The poor countries including Bangladesh have so poor 'understanding about the nature that the most widely discussed greenhouse gas effect or simply the idea of industrial smokes could have been the chief culprit in the development of fatal cataclysms was estimated by our people as environmentalists' eccentricity. Not even before twenty years, the poor nations could recognize the so-called natural calamities as human created phenomena; rather those were to be the atonement for the evils done. However, scientifically intelligent enough but morally denigrated rich western nations across both coasts of the Atlantic engaged themselves in the race of industrial revolution one and half a century ago and still are on run. The forms of wastes are being produced throughout the industrial process virtually pollute all the three phases - solid, liquid and gas - of natural elements. Out of many destructive waste agents, one is acid rain to burn out the fertility of the surface soil and kill the insects.
(Dr. M Abul Kashem Mozumder, Pro-VC, BUP and Dr. Md. Shairul Mashreque, Retired Professor, Chittagong University)