Geography - sustaining ecosystems

Ecosystem

A community of plants and animals (the biotic parts) interacting with each other and with the non-living (abiotic) environment of climate, soil and water. Can be as small as a pond or as large as a rainforest.

Interdependence in an ecosystem

Each part depends on the others: climate decides which plants grow, plants feed animals and build soil through leaf litter, animals pollinate plants and spread seeds, and water carries nutrients. Change one part (remove the trees, say) and everything else changes.

Biome

A global-scale ecosystem such as tropical rainforest or tundra, defined mainly by climate (temperature and rainfall).

Food chain and food web

A food chain passes energy from producers (plants) to consumers (herbivores, then carnivores) and finally decomposers. A food web links many chains and shows how losing one species affects many others.

Nutrient cycle

Nutrients move between three stores – biomass (living things), litter (dead leaves) and soil – through decay, uptake by roots and the fall of leaves. Inputs come from rainfall and weathered rock, losses from leaching and surface runoff.

Polar ecosystems: distribution and climate

The Arctic and Antarctica, inside the polar circles (above about 66°). Very cold (winters of −40°C or below, summers barely above freezing), very dry (precipitation under 250 mm, falling as snow), with six months of darkness and six of daylight.

Polar ecosystems: flora and fauna

Flora: mosses, lichens, algae and low tundra plants at the fringes, no trees. Fauna: polar bears, Arctic foxes, caribou and seals in the Arctic, penguins, seals and whales in Antarctica, all insulated by thick fat, fur or feathers.

Coral reefs: distribution and climate

Shallow, clear, warm seas of 23–29°C between 30° N and 30° S: the Great Barrier Reef, the Red Sea, the Caribbean and Indonesia. They need sunlight, salty water and little sediment.

Coral reefs: flora and fauna

Built by coral polyps living with algae (zooxanthellae) that give them food and colour. Home to about a quarter of all marine species: parrotfish, clownfish, turtles, reef sharks, sea anemones and seaweeds.

Grasslands: distribution and climate

Tropical grassland (savanna) lies between rainforest and desert at 5°–20° (the Serengeti, the Brazilian cerrado): hot, with a wet and a dry season and 500–1,500 mm of rain. Temperate grassland (prairies, steppes, pampas, veld) lies in continental interiors at 40°–60°: hot summers, cold winters and 250–750 mm of rain.

Grasslands: flora and fauna

Savanna: drought-resistant grasses, scattered acacia and baobab trees, zebra, wildebeest, giraffe, elephant and lion. Temperate: tall or short grasses with few trees, bison, prairie dogs and coyotes, now largely ploughed for wheat or grazed by cattle.

Temperate deciduous forest: distribution and climate

At 40°–60° N in western Europe (including the UK), the eastern USA, eastern China and Japan. Mild (−5°C to 25°C), 500–1,500 mm of rain spread through the year and four distinct seasons.

Temperate forest: flora and fauna

Broadleaved trees (oak, beech, ash) that drop their leaves in autumn to save water and energy, layers of shrubs (hazel, holly) and ground plants (bluebells) that flower before the canopy closes. Deer, foxes, badgers, squirrels and woodpeckers on rich, fertile brown earth soils.

Tropical rainforest: distribution and climate

Within about 10° of the equator: the Amazon (Brazil), the Congo Basin, Indonesia and Malaysia. Hot all year (26–28°C, no seasons), over 2,000 mm of rain spread through the year and very humid, with rising air at the ITCZ giving daily convectional storms.

Tropical rainforest: flora and fauna

The most biodiverse ecosystem on Earth, holding over half of all species. Evergreen hardwoods (mahogany, teak), lianas, epiphytes and orchids. Monkeys, sloths, jaguars, toucans, parrots, tree frogs and millions of insect species.

Hot deserts: distribution and climate

Around the tropics (20°–30° N and S) under the sinking air of the Hadley cell: the Sahara, Arabian, Kalahari, Australian, Atacama and Mojave deserts. Under 250 mm of rain a year, daytime temperatures of 40–50°C and nights that can fall below 0°C.

Hot deserts: flora and fauna

Cacti and succulents that store water, plants with very long roots or tiny leaves, and seeds that lie dormant until rain. Camels (fat stored in humps, closing nostrils), fennec foxes (large ears to lose heat), scorpions and reptiles that burrow or come out at night.

Tropical rainforest climate (detail)

Equatorial: an average of about 27°C with a tiny annual range of 2°C but a daily range of about 10°C, over 2,000 mm of rain (Manaus 2,300 mm) falling most afternoons as convectional storms, humidity around 80% and light winds.

Tropical rainforest nutrient cycle

Very fast: constant heat and moisture make leaves fall all year and decompose within weeks. Most nutrients are stored in the biomass (the trees) and very few in the soil, because roots take them up at once and heavy rain leaches the rest away. Clearing the trees removes the nutrient store.

Tropical rainforest soil profile

Latosol: deep (up to 30 m) but infertile. A thin dark humus layer on top, below it red or yellow clay rich in iron and aluminium oxides, heavily leached of nutrients. Most tree roots are shallow because the nutrients are near the surface.

Tropical rainforest water cycle

Heavy rain is intercepted by the canopy and reaches the ground slowly. Trees take up water and return it to the air by transpiration – about half of Amazon rainfall is recycled from the forest itself. Rising moist air forms clouds and convectional rain each afternoon. Deforestation reduces transpiration and therefore rainfall.

Rainforest structure

Emergents (up to 50 m), the dense canopy (30–40 m, where most life is found), an under-canopy of young trees and lianas, a shrub layer and a dark forest floor receiving under 2% of the sunlight.

Plant adaptations in the rainforest

Buttress roots support tall trees in shallow soil, drip-tip leaves shed heavy rain, smooth thin bark lets water run off, lianas climb to reach light, epiphytes grow on branches for light, leaves angle towards the sun and emergents grow fast to the top.

Animal adaptations in the rainforest

Monkeys and sloths with prehensile tails or strong claws for life in the canopy, toucans with big beaks for fruit, poison dart frogs with warning colours, camouflaged chameleons and insects, nocturnal species that avoid the heat and flying squirrels that glide between trees.

Interdependence in the rainforest

The climate allows constant growth, trees shade the soil and recycle nutrients, animals pollinate flowers (orchid bees) and spread seeds (agoutis bury Brazil nuts), decomposers return nutrients and indigenous people use the forest sustainably. Remove the trees and rainfall falls, soils erode, animals lose their habitat and local people lose their livelihoods.

Goods provided by tropical rainforests

Timber (hardwoods), food (bananas, cocoa, coffee, nuts, fruit), medicines (about a quarter of modern drugs come from rainforest plants, such as quinine and the rosy periwinkle used against leukaemia), rubber, oils, minerals, water and hydro-electric power.

Services provided by tropical rainforests

Carbon storage (the Amazon holds around 100 billion tonnes of carbon), oxygen production, regulation of the water cycle and climate, soil protection, biodiversity as a gene bank, tourism and leisure, and homes for indigenous peoples.

Human impact: logging

Hardwoods such as mahogany and teak are sold for furniture and building. Clear felling destroys everything, selective logging still damages many trees around each one removed, and logging roads open the forest to further clearing. Much logging is illegal – at times estimated at up to 80% in Brazil.

Human impact: agriculture

Cattle ranching is the biggest cause of Amazon clearance (about 70–80%), plus soya plantations in Brazil and palm oil in Indonesia. Slash-and-burn and commercial farming leave exhausted soil after a few years, so more forest is cleared.

Human impact: mineral extraction

Open-cast mines for iron ore (Carajás in Brazil, the world’s largest), bauxite and gold strip away the forest. Gold mining pollutes rivers with mercury and brings illegal miners (garimpeiros) onto indigenous Yanomami land. Oil and gas drilling in Ecuador and Peru causes spills.

Human impact: tourism and energy

Mass tourism builds roads and lodges, disturbs wildlife and pollutes. Hydro-electric dams (Belo Monte on the Xingu in Brazil, 2016, flooded about 500 km²) drown forest and displace people. Roads such as the Trans-Amazonian Highway open the forest to settlers.

Scale of deforestation

About 17–20% of the Amazon has been cleared since 1970. Brazil’s annual rate fell from 27,000 km² in 2004 to about 4,500 km² in 2012, rose again to 13,000 km² in 2021 and fell sharply after 2023 under tougher enforcement.

Effects of deforestation

Loss of biodiversity and extinctions / soil erosion, silted rivers and floods / less transpiration so less rainfall / carbon released, adding to climate change / indigenous people lose land and culture / short-term jobs and income but long-term loss of goods and services.

Sustainable management methods

Selective logging and replanting / Forest Stewardship Council (FSC) certified timber / ecotourism / national parks and biosphere reserves / agroforestry / debt-for-nature swaps / international deals such as REDD+ (payments for keeping forest standing) / land rights for indigenous communities.

Biosphere reserve

A UNESCO-designated area with a strictly protected core zone, a buffer zone for research and low-impact activities and a transition zone where people live and farm sustainably, such as the Crocker Range in Sabah, Borneo.

Rainforest management case study: Costa Rica – background

In Central America, about 5 million people. Lost forest fast in the 20th century – cover fell from 75% in 1940 to about 21% by 1987 through cattle ranching and logging. Today forest covers over half the country again, the first tropical country to reverse deforestation.

Costa Rica – Payments for Environmental Services (PES)

Since 1997 the government has paid landowners (about US$64 per hectare a year) to keep, restore or replant forest, funded by a tax on fuel and by water users. Over 1 million hectares have been protected. Payments reward carbon storage, water supply, biodiversity and scenery.

Costa Rica – protected areas and ecotourism

About 26% of the country is national park or reserve (Tortuguero, Corcovado, Monteverde). Ecotourism brings about 3 million visitors a year and roughly 8% of GDP, giving locals jobs as guides, lodge staff and craft sellers, so the forest is worth more standing than cleared.

Costa Rica – local example: Monteverde

The Monteverde Cloud Forest Reserve (1972, 10,500 hectares) is run by a non-profit organisation with the local community: visitor numbers are limited, trails and canopy walkways keep tourists on paths, entry fees fund rangers and research, and locals run the hotels, guiding and coffee farms of the nearby town of Santa Elena.

Costa Rica – successes and problems

Successes: forest cover doubled, a quarter of the land protected, ecotourism jobs, about 98% renewable electricity and a target of carbon neutrality. Problems: tourist pressure and road building near reserves, expanding pineapple and palm oil plantations, dependence of PES on the fuel tax and some continuing illegal logging.

Alternative rainforest case study note

If your school used a different example (Rupununi in Guyana, the Crocker Range Biosphere Reserve in Borneo or the Samasati reserve in Costa Rica), learn that one – the question asks for a named example, its strategies and how successful they are.

Antarctica – characteristics

A continent of 14 million km² (nearly twice the size of Australia) covered 98% by ice up to 4.8 km thick, holding about 70% of the world’s fresh water. The highest, driest, windiest and coldest continent: a record −89.2°C at Vostok, under 50 mm of precipitation in the interior (a polar desert) and winds over 300 km/h. The surrounding sea ice doubles its area each winter.

Antarctica – flora and fauna

Flora: only lichens, mosses, algae and two flowering plants on the Antarctic Peninsula. Fauna live on the coast and in the sea: emperor and Adélie penguins, Weddell and leopard seals, blue and humpback whales and albatrosses, all depending on krill (small shrimp-like animals) that feed on plankton. The largest land animal is a midge.

The Arctic – characteristics

An ocean (the Arctic Ocean, 14 million km²) surrounded by the land of Canada, Alaska, Greenland, Scandinavia and Russia. Sea ice covers the ocean in winter and shrinks in summer. The land is tundra with permafrost. Winter temperatures of −30°C to −40°C, summers up to 10°C, precipitation under 500 mm.

The Arctic – flora and fauna

Tundra plants: mosses, lichens, sedges, dwarf willow and birch and the Arctic poppy – low-growing and quick to flower in the short summer. Animals: polar bears, Arctic foxes and hares, caribou (reindeer), musk ox, walrus, seals, narwhal and bowhead whales and migrating birds. About four million people live in the Arctic, including the Inuit, Sami and Nenets.

Interdependence in Antarctica

Cold nutrient-rich water supports phytoplankton, which feed krill, which feed penguins, seals and whales. Penguin and seal droppings fertilise the few plants on land. Sea ice gives seals breeding platforms and shelters the krill beneath it. Warming water and krill fishing reduce krill, so penguin colonies shrink.

Human activity: scientific research

About 70 research stations run by 30 countries (the UK’s Halley VI and Rothera, the USA’s McMurdo with 1,000 people in summer). Positives: discovery of the ozone hole in 1985 and climate records from ice cores. Negatives: fuel use, waste, buildings and ships that disturb wildlife.

Human activity: tourism

Antarctic tourism grew from a few thousand visitors a year in the 1990s to over 100,000 in 2022–23, mostly on cruise ships to the Peninsula. Arctic cruises visit Svalbard and Greenland. Impacts: trampling of moss, disturbed penguin colonies, oil and sewage from ships, introduced species, but it raises awareness and money for conservation.

Human activity: fishing and whaling

Krill and Patagonian toothfish are fished in the Southern Ocean (the krill catch has been regulated by CCAMLR since 1982). Commercial whaling nearly wiped out blue whales before the 1986 IWC moratorium. Japan hunted under ‘scientific’ permits until 2019, and Norway and Iceland still whale in the Arctic. Overfishing removes food for seals and penguins.

Human activity: mineral exploitation

The Arctic may hold 13% of the world’s undiscovered oil and 30% of its gas (US Geological Survey). Oil at Prudhoe Bay in Alaska and Yamal gas in Russia bring the risk of spills in freezing seas and damage to permafrost. Mining is banned in Antarctica by the 1991 Madrid Protocol.

Human activity: indigenous people

Inuit, Sami and other Arctic peoples have hunted, fished and herded sustainably for thousands of years. Oil and gas, mining and climate change now threaten their hunting grounds, while modern settlement brings jobs and health care but loss of traditional ways of life.

Climate change in the polar regions

The Arctic is warming about four times faster than the global average: summer sea ice has shrunk by about 13% per decade since 1979 and polar bears struggle to hunt. The Antarctic Peninsula has warmed about 3°C in 50 years, ice shelves such as Larsen B (2002) have collapsed and krill numbers have fallen.

Small-scale sustainable management case study: Union Glacier Camp, Antarctica

A seasonal tourist and expedition camp run by Antarctic Logistics and Expeditions in the Ellsworth Mountains, about 1,000 km from the South Pole. Open only from November to January, with a few hundred visitors a year flown in from Punta Arenas in Chile.

Union Glacier – how it is sustainable

All structures are temporary tents taken down each season / all waste, including human waste, is flown out to Chile / solar panels and low-emission fuel reduce energy use / visitors are briefed on Antarctic Treaty rules (no litter, no disturbing wildlife, boots and clothing cleaned to stop seeds and bacteria arriving) / small numbers limit the impact.

Alternative small-scale examples

Whale watching in Iceland and Norway as a profitable alternative to whaling. Svalbard in Norway: tourists limited to marked routes, snowmobile restrictions and strict polar bear protection. The Ice Hotel at Jukkasjärvi in Sweden, rebuilt from river ice every winter and run with Sami tourism.

Global management case study: the Antarctic Treaty

Signed in 1959 by 12 countries (in force from 1961), now with over 50 parties. Antarctica is set aside for peace and science: no military activity, no nuclear tests or waste dumping, all territorial claims frozen, free exchange of scientific data and the right to inspect any base.

Antarctic Treaty – Madrid Protocol (1991)

The Protocol on Environmental Protection, in force from 1998, bans all mining and mineral exploration (reviewable from 2048), requires environmental impact assessments for every activity, protects plants and animals and sets strict rules on waste and sewage.

Antarctic Treaty – how successful?

Successes: Antarctica has stayed peaceful and unexploited for over 60 years, with no mining, and tourism is regulated through IAATO (ships carrying over 500 passengers may not land, no more than 100 people ashore at once, keep 5 m from wildlife). Weaknesses: no enforcement body, fishing and tourism keep growing and climate change is beyond its control.

Arctic Council

Founded in 1996 by the Ottawa Declaration between the eight Arctic states (Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden and the USA) with six indigenous peoples’ organisations as permanent participants. Promotes sustainable development and environmental protection but has no legal powers and does not deal with military matters. Work with Russia was paused after 2022.

Earth Summits

United Nations environment conferences: Rio 1992 (Agenda 21 and the Convention on Biological Diversity), the Kyoto Protocol 1997 and the Paris Agreement 2015 on climate change. They matter for polar regions because warming is the biggest threat to both.