Habitat destruction Revision Notes

An ecosystem is a natural unit consisting of all the living organisms (plants, animals, microorganisms) in a particular area, together with the non-living physical environment (such as soil, water, air, and climate). These components form a system because they interact continuously, influencing each other's survival and functioning.

For example, a pond ecosystem includes fish, algae, insects, water, sunlight, and minerals dissolved in the water. Each part affects the others, creating a balanced system.

• Includes both biotic (living) and abiotic (non-living) components.
• Functions as an integrated system with interactions among components.
• Can vary in size from a small pond to a large forest.

The biotic components of an ecosystem are the community of organisms living together. These organisms interact in various ways:

Competition for resources like food, water, and space.

Predation, where one organism hunts another for food (e.g., a fox hunting rabbits). Mutualism, where both species benefit (e.g., bees pollinating flowers). Parasitism, where one benefits at the expense of another (e.g., ticks on mammals).

• Organisms form a community with complex relationships.
• Interactions affect population sizes and ecosystem health.
• Energy flows through the community via food chains and webs.

Abiotic factors are the non-living parts of the environment that influence living organisms. These include temperature, sunlight, water availability, soil type, and atmospheric gases.

Organisms depend on these factors for survival. For example, plants require sunlight for photosynthesis and water from soil. Changes in abiotic factors can affect the whole ecosystem, such as a drought reducing water availability and stressing plants and animals.

• Abiotic factors shape the habitat conditions.
• They influence which organisms can survive in an ecosystem.
• Abiotic and biotic components interact continuously.

The interactions between organisms and their environment are fundamental to ecosystem function. For example, plants absorb minerals and water from the soil and carbon dioxide from the air to produce food by photosynthesis. Animals depend on plants or other animals for food and shelter.

These interactions create cycles, such as the water cycle and nutrient cycles, which recycle essential elements through the ecosystem.

If one component changes, it can affect others. For instance, pollution can alter water quality, harming aquatic organisms and disrupting the ecosystem balance.

• Organisms depend on abiotic factors for energy and nutrients.
• Ecosystem processes involve cycling of materials between biotic and abiotic parts.
• Disruptions in interactions can destabilise ecosystems.

The balance of interactions within an ecosystem maintains its stability and resilience. Healthy ecosystems support biodiversity, provide resources like food and clean water, and regulate climate.

If interactions are disrupted, for example by habitat destruction or pollution, the ecosystem may lose species, reduce productivity, or collapse.

Understanding these interactions helps in conservation efforts and managing human impacts on ecosystems.

• Interactions maintain ecosystem balance and biodiversity.
• Disruptions can lead to species loss and ecosystem degradation.
• Studying ecosystems aids environmental protection and sustainable use.

Biodiversity describes the range of different species living in a particular area. This includes all types of organisms such as plants, animals, fungi, and microorganisms. It is a measure of how many distinct species coexist in a habitat, reflecting the complexity of life forms present.

For example, a tropical rainforest may contain thousands of species of trees, insects, birds, and mammals, indicating high biodiversity. In contrast, a desert may have fewer species adapted to harsh conditions, showing lower biodiversity.

• Biodiversity focuses on species variety within a specific area.
• It includes all forms of life: plants, animals, fungi, and microbes.
• Higher biodiversity means more species are present.

Species variety is crucial because it supports ecosystem functions and resilience. Diverse species perform different roles such as pollination, decomposition, and nutrient cycling, which maintain ecosystem health.

If a habitat has many species, it is more likely to withstand environmental changes or disturbances. For example, if one species declines due to disease, others can fill its ecological role, preventing ecosystem collapse.

• Species variety supports essential ecosystem processes.
• High biodiversity increases ecosystem stability and resilience.
• Loss of species variety can disrupt ecosystem functions.

Scientists measure biodiversity by counting the number of different species in a habitat, known as species richness. They may also consider species abundance, which is how many individuals of each species are present.

For example, a pond with 10 different species of aquatic plants and animals has higher species richness than a pond with only 3 species. This count helps ecologists assess the health and complexity of ecosystems.

• Species richness is the count of different species present.
• Species abundance refers to the number of individuals per species.
• Both measures help evaluate biodiversity levels.

A coral reef ecosystem is an example of high biodiversity, hosting thousands of fish species, corals, and other marine organisms in a relatively small area.

In contrast, a polar tundra has fewer species adapted to cold conditions, resulting in lower biodiversity. These examples show how biodiversity varies with habitat type and environmental conditions.

• Coral reefs have very high species variety.
• Polar tundra has fewer species adapted to extreme cold.
• Habitat conditions influence biodiversity levels.

Biodiversity is an indicator of ecosystem health. Areas with rich species variety tend to have balanced food webs and efficient nutrient cycling.

Conversely, habitats with low biodiversity may be more vulnerable to invasive species or environmental stress. Maintaining species variety is therefore important for conservation and sustainable ecosystem management.

• High biodiversity indicates a healthy ecosystem.
• Species variety supports balanced food webs.
• Conservation efforts aim to protect biodiversity.

Human populations require space for housing, farming crops, and raising livestock. To meet these needs, natural habitats such as forests, grasslands, and wetlands are often cleared or converted. This process, called land conversion, removes the native vegetation and disrupts the existing ecosystem.

For example, clearing a forest to create farmland destroys the homes of many species, reducing biodiversity. Similarly, draining wetlands for housing development eliminates unique aquatic habitats.

The expansion of urban areas and agricultural land is a leading cause of habitat loss worldwide, as natural areas are replaced by human-dominated landscapes.

• Clearing forests for farmland removes native plants and animals.
• Urban development replaces natural habitats with buildings and roads.
• Livestock grazing can degrade grasslands and reduce plant diversity.

Natural resources such as minerals, fossil fuels, timber, and water are extracted to support human industries and energy needs. Mining operations, logging, and drilling physically alter habitats, often causing fragmentation or complete destruction.

For instance, open-pit mining removes large areas of soil and rock, destroying the surface habitat. Logging removes trees that provide shelter and food for many organisms.

These activities can also cause soil erosion and sedimentation in nearby water bodies, further harming aquatic habitats downstream.

• Mining removes soil and rock, destroying habitats.
• Logging reduces forest cover and disrupts ecosystems.
• Resource extraction often leads to habitat fragmentation.

Pollution from chemicals, waste, and nutrients contaminates rivers, lakes, and oceans, degrading habitats and harming aquatic life. Sources include agricultural runoff, industrial discharge, sewage, and oil spills.

Although detailed eutrophication processes are not required, excess nutrients can cause algal blooms that reduce oxygen levels, stressing or killing aquatic organisms.

Pollution can alter water chemistry, making environments unsuitable for sensitive species and reducing biodiversity in freshwater and marine ecosystems.

• Chemical pollutants poison aquatic organisms.
• Nutrient runoff causes oxygen depletion in water bodies.
• Pollution reduces habitat quality and biodiversity in aquatic systems.

The causes of habitat destruction often interact. For example, land clearing for agriculture can increase soil erosion, which adds sediment to rivers, worsening pollution.

Extraction activities may introduce pollutants or change water flow, affecting both terrestrial and aquatic habitats.

Overall, these causes reduce the area and quality of habitats, leading to declines in species populations and ecosystem health.

• Land use changes can increase pollution and erosion.
• Resource extraction affects multiple habitat types.
• Combined effects lead to loss of biodiversity and ecosystem services.

Biodiversity refers to the variety of different species living in a particular area. When deforestation occurs, large areas of forest are cleared, destroying the habitats that many species rely on for food, shelter, and breeding. This habitat destruction reduces the number of species that can survive in the area, leading to decreased biodiversity.

For example, clearing a tropical rainforest to create farmland removes the complex habitat structure, causing many specialised species to disappear. This loss of biodiversity weakens ecosystem stability and resilience, as fewer species means less variety in ecological roles and interactions.

• Biodiversity decreases because species lose their habitats.
• Specialist species are often the first to be lost.
• Reduced biodiversity affects ecosystem health and function.

When deforestation removes critical habitats, some species cannot adapt or relocate and eventually die out. This leads to local or global extinction. Species with small populations or very specific habitat needs are especially vulnerable.

For instance, the orangutan depends on tropical forest habitats. Large-scale deforestation in Southeast Asia has caused significant population declines, pushing the species towards extinction.

Extinction reduces genetic diversity and can disrupt food chains, causing further ecological imbalance.

• Habitat loss can cause species extinction.
• Species with narrow habitat requirements are most at risk.
• Extinction disrupts ecosystem dynamics.

Trees play a crucial role in maintaining soil quality. Their roots bind soil particles together, preventing erosion by wind and water. When trees are removed, the soil becomes loose and more susceptible to being washed or blown away.

Without tree cover, heavy rainfall can wash away the nutrient-rich topsoil, leading to soil degradation. This reduces soil fertility, making it harder for plants to grow and further damaging the ecosystem.

An example is deforested hillsides where heavy rains cause landslides and loss of productive soil.

• Tree roots stabilise soil and prevent erosion.
• Deforestation exposes soil to erosion by rain and wind.
• Soil degradation reduces land productivity and harms ecosystems.

Trees intercept rainfall and their roots absorb water, reducing surface runoff. When forests are cleared, less water is absorbed and more runs off the surface, increasing the volume and speed of water entering rivers.

This can lead to more frequent and severe flooding downstream. For example, deforestation in river catchment areas often causes flash floods during heavy rainstorms.

Flooding can damage human settlements, agriculture, and natural habitats, creating further environmental and economic problems.

• Trees reduce surface runoff by absorbing water.
• Deforestation increases runoff and flood risk.
• Flooding damages ecosystems and human infrastructure.

Trees absorb carbon dioxide (CO₂) during photosynthesis, storing carbon in their biomass. When trees are cut down and often burned or left to rot, the stored carbon is released back into the atmosphere as CO₂, a greenhouse gas.

This release contributes to the greenhouse effect and global warming. Additionally, fewer trees mean less CO₂ is removed from the atmosphere, worsening climate change.

For example, large-scale deforestation in the Amazon rainforest contributes significantly to global CO₂ emissions.

• Trees act as carbon sinks by absorbing CO₂.
• Deforestation releases stored carbon as CO₂.
• Increased atmospheric CO₂ enhances the greenhouse effect and climate change.

Forests provide habitats for a wide variety of organisms, including plants, animals, fungi, and microorganisms. When deforestation occurs, these habitats are destroyed or fragmented, reducing the available living space and resources for many species. This leads to a decline in biodiversity, which is the variety of different species in an ecosystem.

For example, clearing a tropical rainforest for agriculture removes the complex canopy and understorey layers that many species depend on. Some species may be unable to relocate or adapt quickly enough, resulting in local or global extinction. The extinction of one species can disrupt food chains and ecological interactions, further destabilising the ecosystem.

• Deforestation removes habitats essential for many species.
• Loss of habitat causes population declines and extinction risks.
• Reduced biodiversity weakens ecosystem resilience and function.

Trees and vegetation protect soil by anchoring it with roots and reducing the impact of raindrops on the surface. When trees are removed, the soil becomes exposed to wind and water erosion.

Without roots to hold it in place, topsoil is washed or blown away, leading to soil degradation. This reduces soil fertility and can make the land unsuitable for future plant growth.

For instance, in cleared forest areas on slopes, heavy rain can cause rapid runoff, carrying away nutrient-rich soil and leaving behind poorer subsoil layers.

• Tree roots stabilise soil and prevent erosion.
• Deforestation exposes soil to erosion by wind and water.
• Loss of topsoil reduces land fertility and agricultural potential.

Forests act like sponges, absorbing rainfall and releasing it slowly into rivers and groundwater. When deforestation occurs, less water is absorbed by vegetation, increasing surface runoff.

This rapid runoff can overwhelm rivers and drainage systems, causing more frequent and severe flooding downstream.

An example is the increased flooding in areas downstream of deforested hillsides, where heavy rains lead to flash floods that damage communities and infrastructure.

• Vegetation absorbs and slows rainfall, reducing runoff.
• Deforestation increases surface runoff and flood risk.
• Flooding can cause property damage and soil loss downstream.

Trees absorb carbon dioxide (CO₂) from the atmosphere during photosynthesis, storing carbon in their biomass. When forests are cut down and trees are burned or left to decay, the stored carbon is released back into the atmosphere as CO₂, a greenhouse gas.

This increase in atmospheric CO₂ contributes to the enhanced greenhouse effect, leading to global warming and climate change.

For example, large-scale deforestation in the Amazon rainforest releases millions of tonnes of CO₂ annually, reducing the forest’s role as a carbon sink and exacerbating climate change.

• Trees remove CO₂ from the atmosphere and store carbon.
• Deforestation releases stored carbon as CO₂, increasing greenhouse gases.
• Higher CO₂ levels contribute to global warming and climate change.