Biodiversity means an ecological sachet − the variety of species, their genetic makeup and the natural communities in which they occur. The theme for World Environment Day 2020 is "Celebrate Biodiversity", and will be hosted in Colombia in partnership with Germany. Colombia is one of the largest "Megadiverse" nations in the world to hold 10% of the planet's biodiversity. Since it is part of the Amazon rainforest, Colombia ranks first in bird and orchid species diversity and second in plants, butterflies, freshwater fish, and amphibians.

The air we breathe is a product of photosynthesis by green plants; insects, worms, bacteria and other tiny organisms breaks down wastes and aid in the decomposition of dead plants and animals to enrich soils; more than 90% of the calories consumed by people in this world are produced from 80 plant species; almost 30% of medicines are developed from plants and animals. Some ecosystem services that benefit society are climate security, water purification, pollination and prevention of erosion. To feed such a large population, more land is being transformed from wilderness wildlife in agriculture, mining, lumbering and under areas for humans. Many people around the world depend on these species for their food, shelter and clothing. About 80% of our food supply comes from just 20 kinds of plants.

Some of the health issues influenced by bio-diversity such as, dietary health and nutrition security, infectious disease, medical science and medical resources, social and physiological health and spiritual well being. A wide range of industrial materials are derived directly from biological resources. These include building materials, fibers, dyes, rubber and oil. It plays a part in regulating the chemistry of our atmosphere and water supply.

At the same time, there are a lot of constraints to conserve the forest biodiversity. We are eliminating population of species faster than we can discover new ones. We cut down thousands of acres of virgin forest before we explore what was there. We replace our naturally diverse vegetation with artificial monocultures. We are pulling our environment and changing background of environmental conditions faster than nature can respond.

During the last century, decreases in biodiversity have been increasingly observed. Over the 100 years, Bangladesh has lost about 10% of its mammalian fauna, 3% avifauna and 4% reptile species. IUCN report (2012) has said 58 species of fish, 8 species of amphibians, 63 species of reptiles, 47 species of birds and 43species of mammals in the country which are threatened under degree of risk of extinction.

Studies show that 30% of all natural species will be extinct by 2050. Among the threatened medicinal plant species in Bangladesh, 2 are critically endangered, 2 are endangered, 81 are vulnerable, 109 are conservation dependent and 52 are near threatened species. Percentage of total values are 0.12% is critically endangered, 1.62% endangered, 5.05% vulnerable, 6.79% conservation dependent, 3.24% near threatened, 22.93% not evaluated and 57.26% are least concerned.

The land use pattern of Bangladesh is changing very rapidly. Estimated 25% area of any country should be covered with trees and forest, for many reasons like production of wood, elimination of pollution, green natural environment, healthy air and many others. Bangladesh has 10% of the landmass designated as forests. An estimated 96,000 ha of forest land is encroachment in 2010. Out of 46,000 acres in Madhupur Sal forest, 7,800 acres have been given out to Commercial plantation; 25,000 acres has given into illegal possession. At hilly forest, tobacco farming is increasing rather than the mainstream food. About 10 national and international companies are involved in tobacco farming. In 2000, about 300 hectares land was used which has increased 4232 hectares in 2010. Now the farming area is about 10,000 hectares. Shrimp farming has increased the rate of land encroachment more than double from 45,596 hectares in 2000 to 96,283 hectares in 2010 at Mangrove forest area.

Deforestation and increased road building in the forest are a significant concern as of increased human encroachment upon wild areas, increased resources extraction and further threats to biodiversity. Genetic erosion coupled with genetic pollution may be destroying unique genotypes, thereby creating a hidden crisis which could result in a severe threat to our biodiversity. The recent phenomenon of global warming is also considered to be a major threat to global biodiversity. For example coral reefs which are biodiversity hot spots, will be lost in 20 to 40 years if global warming continues at the current trend.

In addition, cultivation of exotic plant species has become a widespread culture in Bangladesh. Forest areas are not out of intensive cultivation because of land encroachment and growing population rather forest areas are going under the suppression of commercial cultivation because at Sal forest, native plant species like kumbi, koroi, banza, sheura, jalpai, amloki, bohera are being replaced by alien species like rubber, acacia, eucalyptus, pine apple, teak etc. Similarly at Hill forest, native plant species like telsur, garjan, koroi, chapalish, dhundal are being replaced by tobacco, sugarcane, cotton, turmeric, groundnut, maize, teak etc. However, commercial plantation, illegal possession in Sal forest and inappropriate jhumming, illegal logging, stone exploitation, brick fields, Bengali expansionism in Hill forest as well as apiculture, shrimp by catching and animals hunting in Mangrove forest area − all issues are raising a concern about conservation of forest biodiversity. In resulting, land encroachment by local elites or corporate grabbers in the name of agricultural development and industrialization, affects the totality of genetic potential, species and ecosystem stability, degrades the humus and topsoil, changes the food chain, decreases the capability of hydrological cycles and circulation of nutrients as well as the aesthetic value of forest in Bangladesh.

Research mentions, there are a total of 138 different species of wildlife mammals in Bangladesh, 11 of which are now recorded as extinct. Among the existing mammals, 17 species are categorized as Critically Endangered, 12 are endangered and 9 are Vulnerable. The Red List estimates the risk of extinction of a certain species in order to help to set conservation plans and priority. Habitat losses by changing pattern of climate and forest ecosystem as well as human intervention in the forests are considered as some of the primary reasons for the extinction of these species from the country. In 2000, the IUCN published the Red List of Fauna Species in Bangladesh, covering the status of 895 wildlife species under five categories - mammals, birds, amphibians, fish and reptiles. The 2000 list labeled several species, including gangetic gharial, saltwater crocodile, hoolock gibbon, Phayre's leaf monkey, ritha fish, pangas fish and baghair fish, as "critically endangered" due to the loss of their habitat and food scarcity. The new Red List initiative has included two more categories - butterfly and crustacean (snails, crabs and shrimps), and the number of species has been increased to around 1,700.

The species listed as Critically Endangered in Bangladesh are: Bengal tiger, leopard, clouded leopard, Asian elephant, hoolock gibbon, long-tailed macaque, Phayre's leaf monkey, Asiatic black bear, Malayan sun bear, Indian pangolin, Chinese pangolin, Eurasian otter, smooth-coated otter, gaur, sambar, hog deer and Himalayan striped squirrel. Among the 28 species of carnivores found in the country, seven are recorded as Critically Endangered. The species listed as Endangered in Bangladesh are: mainland serow, pig-tailed macaque, common langur, Assamese macaque, capped langur, barking deer, Asiatic wild dog, fishing cat, Indian hare, Bengal slow loris, Oriental small-clawed otter, parti-colored flying squirrel. The species listed as Vulnerable in Bangladesh are: Ganges river dolphin, rhesus macaque, Bengal fox, Asian golden cat, hog badger, yellow-throated marten, binturong, masked palm civet and Malayan giant squirrel.The Living Planet Report, 2017 of WWF reveals that the world populations of wildlife are declined by 58% since 1970 to 2012. On the other hand, the INTERPOL estimates that internationally the illegal wildlife trade is about 10 to 20 billion USD each year.

Bangladesh is one of the mega biodiversity states in this present world and a wide variety of animal diversity is found in the wilderness areas of this country. Article 18A of the Constitution of Bangladesh deals with the protection and improvement of environment and biodiversity and provides, "The State shall endeavor to protect and improve the environment and to preserve and safeguard the natural resources, bio-diversity, wetlands, forests and wild life for the present and future citizens". The Wildlife (Preservations) Order, 1973 was promulgated by the Government of Bangladesh which was further enacted as the Bangladesh Wildlife (Preservation) Act, 1973. Subsequently in order to provide safety and conservation of forest, wildlife and biodiversity the National Parliament has enacted another Act in 2012 i.e., the Wildlife (Preservation and Security) Act, 2012 which has repealed the earlier enactment. At present this legislation is acting as the apex legal document for conservation of wildlife and biodiversity in Bangladesh.

Though all legislations are commonly based on the sovereign decisions made at national levels, states are also bound by the provisions of the world treaties to which they are parties and hence should base their legislations on the provisions of these treaties. The enactment, implementation and enforcement of legislations on the cross-border movement of wildlife animals are performed by the national bodies of individual States. Likewise in Bangladesh, though few areas are protected under the existing laws, a large portion of its wildlife is currently under serious threat.

In this context, Sustainable conservation of forest requires an entirely inclusive approach, combining modern skill and art, government policies and the attachment of local communities, whose lives depends on biodiversity.

Shishir Reza, Environmental Analyst and Associate Member of Bangladesh Economic Association