🌴 The Living World

Ecosystems

An ecosystem is a community of living things together with the non-living environment around them, linked by food chains and nutrient cycles. Producers, such as plants, capture energy from sunlight; consumers eat other organisms; and decomposers break down dead matter and return nutrients to the soil. Because every part of an ecosystem is connected, or interdependent, a change to one part affects all the others.

On a global scale, ecosystems form larger patterns called biomes, which are set mainly by climate. Rainforest grows on the wet equator, deserts form in the dry belts around 30° latitude, grassland and deciduous forest lie between these extremes, and tundra and polar ice cover the coldest regions.

Tropical rainforests

Tropical rainforests have a hot, wet climate, with average temperatures around 27°C every day and more than 2,000 mm of rainfall a year. A rainforest grows in distinct layers: a few emergent trees stand above a dense canopy, which holds most of the wildlife, with a shaded under-canopy below it and very little light reaching the forest floor.

Rainforest soils are poor because most of the nutrients are stored in the plants rather than the ground. Leaf litter decomposes within days, but roots quickly absorb the released nutrients before rain washes them away, a process called leaching. This is why cleared land can only be farmed for a few harvests before it is exhausted.

Deforestation in the Amazon is driven by cattle ranching, soy farming, logging, mining, road building and dams. Its impacts include biodiversity loss, soil erosion, the release of stored CO₂, and the displacement of indigenous peoples, set against the short-term income these activities bring from exports. Sustainable management aims to reduce this damage through selective logging, ecotourism, debt-for-nature swaps, agreements on hardwood use, and protected areas.

Hot deserts (option)

Hot deserts receive under 250 mm of rain a year, and have very hot days but cold nights, with thin sandy soils. Plants adapt by storing water, as succulents do, or by growing long roots to reach water deep underground. Animals often become nocturnal and burrow to escape the daytime heat.

In the Thar Desert case study, opportunities include mineral resources such as gypsum, strong potential for solar and wind energy, irrigated farming along the Indira Gandhi Canal, and desert tourism. Challenges include extreme heat, a persistent water shortage, and poor accessibility across the region's vast distances.

Desertification occurs on the fringes of deserts when climate change combines with overgrazing, over-cultivation and firewood cutting to strip away the vegetation that holds soil in place. Solutions include tree planting, such as the Great Green Wall, drip irrigation, soil management through bunds and rest periods, and appropriate technology that local people can afford to buy and repair.

Cold environments (option)

Polar regions are ice sheets with months of darkness and temperatures near −40°C. The tundra has permanently frozen ground, called permafrost, and a short summer when low shrubs grow. Both environments are fragile: tyre tracks and pipelines can scar the land for decades because plant growth is so slow.

Plants adapt by growing low to the ground with shallow roots above the permafrost, completing their growth quickly during the short summer. Animals adapt through insulation, such as thick fur or blubber, and small ears that lose less heat, or by migrating or hibernating.

In the Svalbard case study, opportunities include coal mining, rich fishing grounds, energy potential and tourism to see the northern lights. Challenges include months of darkness, extreme cold, and high costs. Protection measures include the Antarctic Treaty, which restricts activity there to science, along with national parks, limits on tourist numbers, and careful engineering such as raised buildings and insulated pipelines.