Inland Fisheries

6.2.7.5 Ecological degradation of beels

The ecological degradation of beels started with the arrival of the water hyacinth a century ago. Rampant growth of this fast-growing weed obstructs the penetration of sunlight, inhibiting planktonic growth and contributing to eutrophication by slowing down water currents and depositing debris at the bottom. The second phase of enhanced eutrophication resulted from the construction of embankments along almost the entire length of the river Brahmaputra and many of its tributaries after the devastating earthquake of 1950. These levees substantially reduced the periodic flushing by monsoon floods. The final onslaught on the wetlands has been from human activities such as buffalo and cattle rearing, agriculture and horticulture, and overfishing. These have resulted in further siltation and damage to the microflora and water quality. The injudicious use of pesticides in farming activities has resulted in the accumulation of residue through surface runoff, leading to the problem of biomagnification. Freshwater dolphins, crocodiles, winter monitor lizards and various species of turtles that were abundant in various beels, are either extinct or highly endangered. A number of fish species, such as Puntius jerdoni, Begarius bagarius and Semiplotus semiplotus are on the verge of extinction. Biodiversity can be an important component in the economic valuation of the wetlands. The change in biodiversity has implications for the food security and livelihood of the population that depends on the beels. The economic value of the biodiversity has not yet been studied. Information on ecological interrelationships between changes in biodiversity and changes in the primary productivity of the beels is required to establish appropriate policies for in situ and ex situ conservation and for other environment related initiatives.