Ecosystem Diversity

South Asia is bordered in the south by the Indian Ocean, in the South-east by Bay of Bengal and in the South-west by the Arabian Sea. Occupying a major portion of the Indo-Malayan realm and a smaller portion of the Palearctic realm, the region is representative of five of the fourteen major ecological regions called biomes, which demonstrate the biodiversity and vegetation patterns of the region as determined by climate, water, geology, soil and diverse topography. South Asia’s topography consists of an amazing variety of mountains, plateaus, dry regions, intervening structural basins, beaches, glaciers, rain forests, deserts, grasslands, etc which creates highly diverse ecosystems. It varies from world highest point, the Mount Everest to the world lowest, the sea beach.

A monsoon climate, characterized by wet summers and dry winters, generally prevails over South Asia. The south-west monsoons (late May to October) bring the maximum rainfall, followed by the north-east monsoons. Precipitation and climate vary significantly from place to place in different countries within the region due to the variations in land forms. Rainfall ranges from 200 mm in the desert areas of the north-west to 4000 mm in the higher Himalayas of Bhutan. The climate also varies from the semi-arid in Pakistan to the tropical monsoon and hot-dry, humid-dry in the rest of the region. The region’s temperature varies ranging from as low as -20 °C in the cold desert to scorching 48 °C desert areas in some plains.

Some of the world’s largest river systems are in the South Asia. The Indus River originates in China and flows to Pakistan. The Ganga and Brahmaputra rivers that originate partly in China, Nepal and Bhutan, and flow to India and Bangladesh. The Indus River is one of the world’s greatest, measuring 2,800 km from its source to sea. The Ganga stretches to about 2,525 km, and the brahmaputtra, the third great Himalayan river, stretches about 2, 900 km flowing through Tibet, India and Bangladesh. There are many other minor rivers originate from great Himalayan drain into Bangladesh through Nepal and India. There are 103 rivers draining in a radial pattern from central highland of Sri Lanka. The Ganga, Brahmaputtra and Meghna are the major rivers in Bangladesh. The rivers in Bhutan are the Jadalkha, Torsa, Raidak, Sankosh, Mao Khola/Aie, and the Manas. Maldives does not have any rivers.

The diversity in the latitude, altitude, climate and topography has resulted in a variety of vegetation in the region, ranging from the temperate and the tropical to the desert vegetation..