Protecting ecosystems

One change leads to another

In nature, a small change rarely stays small. If pollution kills the plants in a pond, less oxygen is produced and fish die; with fewer fish to eat them, insects multiply and spread to nearby farms, and farmers turn to pesticides, which harm the environment further.

A real example: in the 1980s India exported large numbers of frog legs, mainly of the Indian bullfrog. As frogs declined, the insects they eat multiplied into farm pests, so farmers used more synthetic pesticides, harming soil, water and health. The Government of India then banned the export of frog legs.

An ecosystem is balanced when the way its members interact keeps both populations and resources steady. That balance is dynamic: it keeps shifting and can be upset by natural or human-made changes.

Relationships that keep the balance

Organisms compete for food, water, space and sunlight, and this competition keeps any one species from multiplying out of control. Other relationships matter too. In mutualism both gain, like a honeybee getting nectar while pollinating a flower. In commensalism one gains and the other is unaffected, like an orchid supported by a tree. In parasitism one gains and the other is harmed, like a tick feeding on a dog’s blood. The wildlife biologist A.J.T. Johnsingh showed in Bandipur National Park that tigers and leopards depend on healthy populations of prey such as deer and wild boar.

What ecosystems give us

Forests give fresh air, fertile soil, food, fibre, timber and medicines; ponds, rivers and lakes give water and food; and all of them have beauty and recreational value. Overusing or misusing these resources upsets the balance on which we depend.

The Sundarbans under threat

The Sundarbans, where the Ganga and Brahmaputra meet the sea between India and Bangladesh, is the largest mangrove forest in the world and home to many endangered plants and animals. Its trees break the force of storm winds, waves and floods, and take in carbon dioxide. UNESCO declared it a World Heritage Site in 1987. Yet mangroves are cut for fuelwood and farming, animals are hunted illegally, and industrial waste and sewage pollute its rivers.

Protected areas

Protected areas are stretches of land or water kept aside to protect wildlife and their homes: national parks, biosphere reserves, wildlife sanctuaries and community conserved areas. They protect entire habitats, including endangered animals and rare plants, for future generations.

Farming in harmony with nature

Fish ponds, farms and parks are human-made ecosystems that need human care. After a food crisis between 1950 and 1965, tractors, synthetic fertilisers and pesticides raised production in the Green Revolution. But long-term overuse reduces soil microbes and humus, so soil erodes; it kills natural predators of pests, and pests become resistant; heavy irrigation drains groundwater; and monoculture cuts biodiversity and harms pollinators. Organic and natural farming, compost and organic manure, such as Kunapa Jala described in the ancient text Vrikshayurveda, crop rotation and natural pest control help protect the soil and our food security.

Read on: ecosystems and interactions, food chains and decomposers, the chapter notes and the NCERT solutions.