Ecosystems under threat Revision Notes

Ecosystems are communities of living organisms interacting with each other and their physical environment. When ecosystems become endangered, their natural balance is disrupted, often due to human activities. Understanding the causes and effects of ecosystem endangerment is essential to managing and conserving natural environments.

• Ecosystems include biotic (living) and abiotic (non-living) components.
• Endangerment occurs when habitats are altered or destroyed.
• Human activities are the primary drivers of ecosystem threats.

Several human activities directly threaten ecosystems by changing or destroying habitats. Three key causes are wetland drainage, intensive agricultural practices, and deforestation.

Wetland drainage involves removing water from marshes, swamps, or bogs to convert the land for agriculture or urban development. This destroys aquatic habitats and alters water cycles.

Intensive agriculture uses high inputs of fertilisers, pesticides, and often monoculture cropping. This reduces habitat diversity, depletes soil nutrients, and can cause pollution, all of which harm local ecosystems and species diversity. For example, planting only one crop type over large areas limits food and shelter variety for wildlife, reducing species richness in the area. Intensive livestock farming can also compact soil and reduce vegetation cover, further degrading habitats.

• Wetland drainage removes aquatic habitats and alters hydrology.
• Intensive agriculture reduces habitat diversity and soil quality.
• Deforestation removes tree cover, disrupting habitats and microclimates.

Deforestation is the large-scale removal of trees, often for timber, agriculture, or urban expansion. Trees provide shelter, food, and breeding sites for many species. Removing them fragments habitats and exposes soil to erosion.

For example, clearing tropical rainforests for cattle ranching destroys complex ecosystems that support thousands of species. The loss of canopy cover changes temperature and moisture levels, making the environment less suitable for many organisms.

Deforestation also interrupts carbon storage, contributing to climate change, which further stresses ecosystems.

• Trees support diverse species and regulate microclimates.
• Removing trees fragments habitats and increases soil erosion.
• Deforestation contributes to climate change, impacting ecosystems further.

Biodiversity refers to the variety of species in an ecosystem. When habitats are destroyed or degraded, fewer species can survive, leading to biodiversity loss.

Genetic depletion occurs when populations shrink and genetic diversity within species declines. This reduces their ability to adapt to environmental changes or resist diseases.

For example, a small isolated population of frogs in a drained wetland may have limited genetic variation, making them vulnerable to new pathogens or climate shifts. Reduced biodiversity also weakens ecosystem resilience, making recovery from disturbances harder.

• Biodiversity loss means fewer species and simpler ecosystems.
• Genetic depletion reduces species' adaptability and survival chances.
• Healthy ecosystems require diverse species and genetic variation.

Extinction is the permanent loss of a species from an ecosystem. It occurs when populations become too small or habitats disappear entirely.

Extinctions disrupt food chains and ecological interactions. For example, losing a pollinator species can reduce plant reproduction, affecting other animals relying on those plants.

Extinction reduces ecosystem services such as pollination, water purification, and soil fertility, which humans also depend on. Preventing extinction requires protecting habitats and maintaining biodiversity.

• Extinction is irreversible loss of species.
• It disrupts ecological relationships and ecosystem functions.
• Protecting habitats helps prevent species extinction.