CBSE Notes Class 7 Science Chapter 12 Forests : Our Lifeline

Forests cover approximately one-third of the Earth's land surface, acting as a critical resource for sustaining life on the planet. The type of forest in a particular region is determined by several factors, including climate, topography, and soil type. These factors influence the variety of trees, plants, and animals that thrive in a forest ecosystem, making each forest unique.

1.0Forest Structure

• Forests are composed of a diverse range of trees, such as teak, sal, shisham, neem, bamboo, and others. 
• Along with trees, forests also host shrubs, herbs, climbers, and creepers. In dense forests, the forest floor is often dark due to the thick canopy formed by the branches of tall trees, which block sunlight. 
• This shaded environment allows mosses, lichens, and shade-loving plants to grow.
• The branches of tall trees form the upper canopy, creating a roof over the forest. Beneath the canopy are several horizontal layers known as the understorey, which consists of smaller trees, shrubs, and ground-level plants. 
• This layered structure creates distinct habitats at different heights, contributing to the rich biodiversity of forest ecosystems.

2.0Uses of Forests

Forests are invaluable to life on Earth, providing a wide range of benefits, including:

• Food Production : As primary producers, plants form the base of the food chain, supplying energy to all living organisms.
• Resources : Forests provide materials such as wood, fuel, medicines, paper, rubber, and fibers used in clothing.
• Wildlife Habitat : Forests offer shelter and protection to numerous animal species.
• Climate Regulation : They play a vital role in controlling global temperatures and the water cycle, influencing rainfall patterns.
• Soil and Water Conservation : Tree roots help prevent soil erosion by binding the soil, and forests act as natural filters for water, maintaining water quality and the water table.
• Carbon Balance : Forests help balance carbon dioxide (CO2) and oxygen (O2) levels by absorbing CO2 and releasing oxygen during photosynthesis.
• Air Quality : By absorbing pollutants, forests contribute to cleaner air.
• Flood Control : Forests reduce the risk of floods by absorbing rainwater and allowing it to seep into the ground slowly.
• Recreation and Tourism : Forests serve as places of leisure and recreation, attracting tourists.
• Noise Reduction : The thick foliage of forests absorbs sound, reducing noise pollution.

3.0Interdependence of Plants and Animals

• Forests play a crucial role in maintaining biodiversity by supporting a variety of plants and animals. 
• The interconnectedness of living organisms in forests creates a biotic community, where each organism relies on others for survival.
• Plants are autotrophic, meaning they produce their own food through photosynthesis, while animals are heterotrophic, depending on plants and other animals for nourishment. Herbivores consume plants, carnivores eat other animals, and omnivores consume both. This dynamic relationship creates food chains, illustrating the flow of energy within ecosystems. 
• For example, a rat may eat grains, a snake consumes the rat, and an eagle preys on the snake. This chain of relationships continues when organisms die and decompose, returning nutrients to the soil for plants to use again.

4.0Food Webs and Decomposers

• While food chains represent a simple flow of energy, food webs show a more complex and interconnected system. 
• Several food chains overlap, illustrating how different species interact within an ecosystem. 
• For instance, a cat might eat both rats and hens, while a wolf can also prey on the same animals, showing the interconnectedness of nature.

• Decomposers such as bacteria and fungi are essential for recycling nutrients in a forest. These organisms break down dead plants and animals, converting them into simple nutrients that enrich the soil. 
• This process ensures that nutrients are available for new plants to grow, maintaining the balance of life within the forest.

Balance in Nature

• Maintaining balance in ecosystems is crucial for the survival of all species. 
• If one species becomes too abundant, it can disrupt the ecosystem. 
• For instance, an overpopulation of lions could decimate deer populations, while an excess of deer might deplete the grass supply, affecting other herbivores. 
• Hence, a balance is necessary to ensure the survival and co-existence of various species.

Mutual Dependence of Plants and Animals

• Animals rely on plants for food, shelter, and oxygen. 
• Plants, through the process of photosynthesis, release oxygen, which animals use for respiration. 
• Additionally, many animals, such as birds and insects, find shelter in trees, making their homes in tree holes or building nests among branches.
• Conversely, plants depend on animals for carbon dioxide, which animals release during respiration. 
• Pollination, essential for plant reproduction, often occurs with the help of insects, birds, and bats. Seed dispersal, another crucial aspect of plant reproduction, is frequently aided by animals that eat fruits and carry the seeds to new locations.

5.0The Impact of Deforestation

• Climate Change : Large-scale deforestation disrupts local weather patterns and contributes to global climate change by increasing greenhouse gas emissions.
• Loss of Biodiversity : Deforestation destroys habitats, threatening the survival of many species.
• Resource Depletion : The removal of forests leads to the loss of valuable resources such as timber, medicinal plants, and other forest products.
• Flooding and Erosion : Without tree cover, the risk of soil erosion and flooding increases, causing damage to ecosystems and human settlements.
• Disruption of Water Cycles : The removal of trees affects the water cycle, reducing the amount of water absorbed by the soil and disrupting the flow of streams and rivers.

6.0Forest Conservation

• Afforestation : Planting new trees to replace those that have been cut down. Communities should be encouraged to plant trees for their everyday needs, rather than destroying existing forests.
• Planned Cultivation : Forests should not be entirely cleared for agriculture, as this can lead to soil erosion and land degradation.
• Prevent Illegal Logging : Laws must be enforced to stop illegal logging, which has led to significant forest loss.
• Prevent Overgrazing : Livestock should be prevented from overgrazing in forest areas, as this can harm young plants and degrade the ecosystem.
• Forest Fire Prevention : Forest fires, whether caused by human activity or natural occurrences, pose a serious threat to both wildlife and nearby communities. Fire prevention measures include using fire retardants and controlling human activities that may spark fires.