Maarg Manthan · Topic 4.8

Human-Modified Ecosystems

Environment & Ecology › Terrestrial and Aquatic Ecosystems · Topic 4.8

Human-modified ecosystems, also called anthropogenic or artificial ecosystems, are ecosystems created or heavily changed by human activity to meet human needs. The main kinds are agro-ecosystems such as croplands, plantations, orchards and fish ponds, urban ecosystems of cities, reservoirs and canals, and managed forests and rangelands. They differ from natural ecosystems in having lower species diversity, simpler food webs, dominance by chosen species, large inputs of energy as fertiliser, fuel and labour, and a need for continuous human management. They often have high productivity of useful crops but depend on subsidies and cause pollution, soil loss and loss of biodiversity. Urban ecosystems have heat islands, air and noise pollution, and heavy import of food, water and energy.

5 min read · UPSC Prelims · Environment & Ecology · Terrestrial and Aquatic Ecosystems

At a Glance

Created by Humans
Types Agro, urban, reservoirs
Biodiversity Low
Inputs Energy subsidies
Urban effect Heat island
Exam link UPSC Prelims, Environment & Ecology: Terrestrial and Aquatic Ecosystems

Where Does It Fit?

This is the last topic of the macro on terrestrial and aquatic ecosystems. It looks at ecosystems that people have made or changed, which links with the later macros on resources, pollution and sustainability. Previous topic: Sea-Grass and Seaweeds. Next topic: Concept of Biogeochemical Cycle: Parts and Types.

What Are Human-Modified Ecosystems and How Do They Differ?

Feature	Natural and human-modified ecosystems
Origin	Natural ecosystems develop without human design. Human-modified ecosystems are created or managed by people, such as farms, plantations, cities and dams
Biodiversity	Natural ecosystems have high diversity. Human-modified ones have low diversity, often a monoculture (single crop)
Food web	Simple in artificial systems with few species and short chains
Energy	Natural: solar energy only. Artificial: extra energy subsidies as fuel, fertiliser, irrigation and machinery
Nutrient cycling	Open and leaky in farms, as nutrients are removed in harvest and added as fertiliser
Stability	Low, with pest outbreaks and need for constant management
Self-regulation	Weak. Humans control species composition, water and pests

What Are the Main Types and Environmental Effects?

Agro-ecosystems: croplands (rice, wheat), plantations (tea, coffee, rubber), orchards, aquaculture ponds, and livestock systems; high yield but with use of pesticides and fertilisers
Urban ecosystems: cities and towns; dominated by buildings, roads and people; need imported food, water and energy and create waste
Urban heat island: cities are warmer than surroundings by several degrees because of concrete, asphalt and less vegetation
Reservoirs and canals: dams create lakes that change river flow and habitats
Managed forests: plantations of teak or eucalyptus with fewer species than natural forests
Impacts: soil erosion, salinisation, eutrophication, pesticide pollution, loss of habitat and greenhouse gas emissions
Benefits: food, fibre, energy, shelter and economic value
Sustainable management: agroforestry, organic and natural farming, integrated pest management, green infrastructure and urban forests

What Else Should You Remember?

Monoculture risk: uniform crops are vulnerable to disease, as in the Irish potato famine of 1845 to 1849
Green Revolution: high yielding varieties raised yields but needed more water and chemicals
Energy ratio: modern farms use more energy as input than they provide as food in some cases
Agroforestry: combining trees and crops
Rice paddy: a wetland-like system and a source of methane
Shifting cultivation: jhum in north-east India
Urban green spaces: parks, roof gardens and urban forests
Urban wetlands: Kolkata East wetlands treat sewage naturally
Waste: cities produce solid waste and sewage
Air quality: vehicles and industry cause pollution
Noise: a feature of cities
Urban biodiversity: sparrows, crows, pigeons, rats and some adaptive species thrive
Artificial wetlands: reservoirs and ponds can host waterbirds
Novel ecosystems: new combinations of species in altered habitats
Land use change: a major driver of biodiversity loss
Ecological footprint: the area needed to support a city’s consumption
Smart cities and sponge cities: designs that manage water and heat
Link: see Land, Forest and Soil Resources macro
Link to waste: see Waste Management macro
Link to pollution: see Air, Marine, Noise and Other Pollution macro
Caution: human-modified does not mean without value, as many support wildlife
Reservoir effects: dams trap sediments, change temperature and block fish migration, but create new habitats for waterbirds
Aquaculture: shrimp ponds replaced mangroves in some coasts
Urban flooding: paved surfaces cut infiltration and raise run-off
Green revolution regions: Punjab and Haryana show high yield but groundwater fall
Green building: buildings with natural cooling lower energy use
Waste heat: vehicles and air conditioners add heat in cities
Exam hint: compare natural and artificial systems on diversity, energy input, stability and nutrient cycling
Ecosystem approach: land use planning that keeps wildlife corridors across farms and towns keeps connectivity

Why Does It Matter for the Exam?

Features: low diversity, energy subsidies
Types: agro, urban, reservoirs
Heat island: urban
Current affairs link: urban forests and sponge cities
Common errors: saying artificial ecosystems are self-sustaining or highly diverse

As an analytical point, most of the world’s land is now modified by people, so conservation must include farms and cities. Wildlife-friendly farming and green infrastructure can raise biodiversity within human landscapes.

Why Is This Topic Important?

Features Simple, managed
Types Agro, urban
Fix Sustainable methods

What Came Next?

The next macro covers nutrient cycling, beginning with the concept of a biogeochemical cycle. Next topic: Concept of Biogeochemical Cycle: Parts and Types.

Key People and Terms

Agro-ecosystem Farm ecosystem
Monoculture Single crop
Energy subsidy Human energy input
Heat island Warmer city
Agroforestry Trees with crops
Novel ecosystem New species mix

Exam Corner

Points to Remember

Artificial ecosystems have low diversity.
They need energy subsidies.
Monoculture is vulnerable to pests.
Cities form heat islands.
Agroforestry mixes trees and crops.

Do Not Confuse With

Natural and agro-ecosystem Solar-driven diverse versus subsidised simple
Monoculture and polyculture One crop versus many
Heat island and greenhouse effect Local city warming versus global warming

Memory Hook

Man-made means managed: few species, fuel and fertiliser inputs, pests and heat in the city.

Mains Angle

Questions ask for features and examples. These points help.

Types Agro, urban
Impacts Pollution, loss
Solutions Sustainable

A Question You May Face

An original practice question, not a past paper question.

“What are human-modified ecosystems? Discuss their characteristics and environmental impacts, and suggest ways of making them sustainable.”

How to Answer

Define Artificial systems.
Types Agro, urban.
Impacts List.
Solutions Green methods.

GS Relevance

Prelims: features and examples of artificial ecosystems, urban heat island. GS Paper 3: ecology and sustainable development.

Frequently Asked Questions

What are human-modified ecosystems?

Human-modified ecosystems, also called artificial or anthropogenic ecosystems, are ecosystems that people have created or greatly altered for their own use. They include croplands, plantations, fish ponds, reservoirs, cities and managed forests. They have fewer species than natural ecosystems and need continuous human management and energy inputs.

What is an agro-ecosystem?

An agro-ecosystem is an ecosystem managed for agriculture, such as a cropland, orchard, plantation or pasture. It has few species, usually a single crop, receives extra energy from fertilisers, irrigation and machinery, and is regularly harvested, so it needs constant management and is more vulnerable to pests than natural systems.

What is the urban heat island effect?

The urban heat island effect is the higher temperature found in cities compared with surrounding rural areas. It is caused by concrete, asphalt and buildings that absorb and store heat, less vegetation and evaporation, and heat from vehicles and air conditioners. It increases energy use and health risks during heat waves.

Why are monocultures risky?

Monocultures are risky because all plants are genetically similar, so a single pest or disease can spread quickly and destroy the whole crop, as the potato blight did in Ireland in the 1840s. They also reduce soil health and biodiversity and need heavy use of chemical inputs.

How can human-modified ecosystems be made more sustainable?

They can be made more sustainable by practices such as agroforestry, crop rotation and mixed cropping, organic and natural farming, integrated pest management, water-saving irrigation, and in cities by creating green spaces, urban forests, rainwater harvesting, waste recycling and wetlands that treat sewage.

PYQ Practice — Statement Analysis

1 Agro-ecosystems have lower species diversity than natural ecosystems.

True

Often a single crop.

2 Artificial ecosystems do not need energy inputs.

False

They rely on energy subsidies.

3 Cities are generally warmer than surrounding areas.