Monsoon, forests and wildlife

The Tropic of Cancer runs through the middle of India: the south is tropical, with high temperatures all year; the north has an extreme climate with a high daily and annual range.

They shield the subcontinent from the cold northern winds from near the Arctic circle, and trap the monsoon winds so that they shed their moisture within India.

Land heats and cools faster than the sea; this difference creates pressure zones that reverse the monsoon winds with the seasons.

Coasts have an equable climate — Mumbai and the Konkan coast hardly know extremes — while interior places such as Delhi, Kanpur and Amritsar have strong seasonal contrasts.

Temperature falls with height: Agra and Darjiling are on the same latitude, but January averages 16 °C in Agra and only 4 °C in Darjiling.

The windward sides of the Western Ghats and Assam get heavy rain in June–September, while the southern plateau, on the leeward side of the Ghats, stays dry.

The Inter Tropical Convergence Zone is a low-pressure belt where trade winds meet. In July it lies around 20°N–25°N over the Gangetic plain — the monsoon trough — and draws the south-east trades across the equator (between 40°E and 60°E), where the Coriolis force turns them into the south-west monsoon.

Once the westerly jet stream withdraws from the north Indian plain, an easterly jet stream sets in along 15°N; it is held responsible for the burst of the monsoon.

If rain fails for one or more weeks after a few rainy days, it is a break in the monsoon. In the north it happens when rain-bearing storms along the trough are few; on the west coast, when winds blow parallel to the coast.

A warm current that appears off Peru every three to seven years, bringing droughts and floods around the world. India uses it to forecast long-range monsoon rainfall; in 1990–91 it delayed the monsoon’s onset by five to twelve days. The IMD forecasts the monsoon using 16 indicators.

In summer the mercury occasionally touches 55 °C in western Rajasthan; in winter it drops as low as −45 °C around Leh.

On the same June day Churu in Rajasthan may record 50 °C or more, while Tawang in Arunachal Pradesh hardly reaches 19 °C.

On a December night Drass in Ladakh may fall to −45 °C, while Thiruvananthapuram or Chennai records 20 °C or 22 °C.

In Kerala and the Andaman Islands day and night may differ by only 7–8 °C; in the Thar desert a 50 °C day can fall to 15–20 °C at night.

Cherrapunji and Mawsynram in the Khasi Hills get over 1,080 cm of rain a year; Jaisalmer rarely gets more than 9 cm.

Tura in the Garo Hills may receive in a single day as much rain as Jaisalmer gets in ten years.

India’s wetlands cover 3.9 million hectares, about 70% of it under paddy. NCERT groups them into eight categories, from the reservoirs of the Deccan and the lagoons of the southern west coast to the mangroves of the Andaman and Nicobar Islands.

India adopted a forest policy in 1952, modified in 1988. It aims to bring 33% of the geographical area under forest cover, conserve biodiversity, check soil erosion and floods, and involve people — especially women — in planting trees.

Managing and planting trees on barren land for environmental, social and rural development. The National Commission on Agriculture (1976) divides it into urban, rural (agro- and community) and farm forestry.

About 4–5% of all known plant and animal species are found in India. The Wildlife Act of 1972 (amended in 1991) protects endangered species and gives legal backing to national parks and sanctuaries; NCERT counts 107 national parks and 573 wildlife sanctuaries.

Launched in 1973 in nine tiger reserves (16,339 sq. km); now 58 tiger reserves with 84,487 sq. km of core habitat in 18 states. Tigers rose from 1,411 in 2006 to 3,682 in 2023 — more than 75% of the world’s tigers.

Launched in 1992 to help states with free-ranging wild elephants ensure their long-term survival; it runs in 18 states. Other projects protect crocodiles, the hangul and the Himalayan musk deer.