Conservation of biodiversity

What you'll learn

This revision guide covers conservation of biodiversity as specified in the CIE IGCSE Biology syllabus. You'll learn why biodiversity is important, the threats it faces, and the methods used to conserve species and ecosystems. This topic connects ecology with human activities and sustainable development, making it essential for both exam success and real-world understanding.

Key terms and definitions

Biodiversity — the variety of all the different species of organisms on Earth, or within a particular ecosystem

Conservation — the protection and management of species and ecosystems to maintain biodiversity

Endangered species — a species whose numbers have fallen so low that it is at risk of extinction

Extinction — the permanent loss of all members of a species from Earth

Habitat destruction — the process by which natural habitat is damaged or removed, making it unable to support the species present

Sustainable development — development that meets the needs of people today without damaging the environment for future generations

Captive breeding programme — breeding endangered species in controlled environments such as zoos to increase population numbers

Seed bank — a store of seeds from different plant species, preserved for future use if species become extinct in the wild

Core concepts

Why biodiversity is important

Biodiversity provides numerous benefits to humans and maintains the stability of ecosystems:

Ecological stability: Ecosystems with high biodiversity are more stable and resilient to environmental changes. Different species play varied roles, so if one species declines, others can maintain ecosystem functions.

Food security: We depend on a variety of plant and animal species for food. Wild relatives of crop plants contain genes that could be used to develop improved crop varieties resistant to disease or climate change.

Medicinal resources: Many medicines originate from plants and animals. For example, aspirin was originally derived from willow bark, and anticancer drugs have been developed from the rosy periwinkle plant found in Madagascar.

Economic value: Biodiversity supports industries including agriculture, fishing, forestry and tourism. Ecotourism in countries like Kenya and Costa Rica generates significant income.

Cultural and aesthetic value: Many species and natural areas have cultural importance to different communities and provide recreational opportunities.

Threats to biodiversity

Human activities pose the main threats to biodiversity globally:

Habitat destruction is the primary cause of biodiversity loss:

• Deforestation for agriculture, timber, or urban development removes natural habitats
• Tropical rainforests are particularly affected, yet they contain over 50% of terrestrial species
• Wetland drainage for farming destroys important breeding grounds for birds and amphibians
• Coral reefs are damaged by coastal development, pollution and destructive fishing practices

Climate change affects species distribution and survival:

• Rising temperatures force species to migrate to cooler regions or higher altitudes
• Some species cannot adapt quickly enough to changing conditions
• Coral bleaching occurs when sea temperatures rise, causing coral polyps to expel their symbiotic algae
• Changes in rainfall patterns affect plant growth and animal migrations

Pollution damages ecosystems directly and indirectly:

• Pesticides and herbicides harm non-target species
• Plastic pollution affects marine animals through ingestion and entanglement
• Eutrophication from fertiliser runoff reduces oxygen levels in water bodies
• Air pollution contributes to acid rain, which damages forests and aquatic ecosystems

Hunting and overharvesting reduce population numbers:

• Illegal poaching threatens elephants, rhinos and tigers
• Overfishing depletes fish stocks, disrupting marine food webs
• Collection of rare plants and animals for the pet trade threatens wild populations

Introduction of invasive species disrupts native ecosystems:

• Non-native species may outcompete native species for resources
• They may lack natural predators in their new environment
• Examples include grey squirrels outcompeting red squirrels in the UK
• Invasive plants like Japanese knotweed damage infrastructure and displace native flora

Conservation methods for endangered species

Several strategies help protect species from extinction:

Legal protection:

• International agreements like CITES (Convention on International Trade in Endangered Species) restrict trade in endangered organisms
• National laws prohibit hunting or collecting protected species
• Marine Protected Areas and National Parks provide legal protection to habitats
• The UK Wildlife and Countryside Act protects native species and their habitats

Captive breeding programmes:

• Breeding endangered species in zoos and wildlife centres increases population numbers
• Genetic diversity is carefully managed to maintain healthy populations
• Once numbers are sufficient, individuals may be reintroduced to the wild
• Examples include the Arabian oryx, which was extinct in the wild but successfully reintroduced
• The California condor population recovered from just 27 individuals through captive breeding

Seed banks:

• Seeds from thousands of plant species are dried and stored at low temperatures
• The Millennium Seed Bank at Kew Gardens stores over 2.4 billion seeds
• Seeds remain viable for decades or centuries
• If species become extinct in the wild, seeds can be germinated to restore populations
• Particularly important for crop wild relatives and medicinal plants

Sperm banks and tissue banks:

• Frozen sperm, eggs and embryos preserve genetic material
• Tissue samples can be used for genetic research
• These methods are especially valuable for species with low reproductive rates
• The Frozen Ark project stores DNA and cells from endangered animals

Habitat conservation and management

Protecting and managing habitats is essential for long-term biodiversity conservation:

Nature reserves and protected areas:

• Designated areas where wildlife and habitats are protected from development
• Rangers monitor and manage the area to maintain biodiversity
• Human activities may be restricted or controlled
• Examples include the Galapagos Islands, Yellowstone National Park, and UK Sites of Special Scientific Interest (SSSIs)

Reforestation and habitat restoration:

• Replanting trees in deforested areas recreates habitat
• Restoring wetlands provides breeding sites for amphibians and birds
• Creating wildlife corridors connects fragmented habitats, allowing species movement
• Removing invasive species allows native species to recover

Sustainable management of existing habitats:

• Controlled grazing maintains grassland habitats without overgrazing
• Coppicing (cutting trees to ground level) in woodlands promotes biodiversity by creating varied light conditions
• Rotation of crops and use of hedgerows on farmland provides habitat for wildlife
• Sustainable fishing quotas prevent overfishing while allowing fishing to continue

Sustainable development and resource use

Balancing human needs with environmental protection is crucial:

Sustainable forestry:

• Selective logging removes only mature trees, maintaining forest structure
• Replanting ensures forest regeneration
• Certification schemes like FSC (Forest Stewardship Council) identify sustainably sourced timber
• Reduces habitat destruction while providing timber resources

Sustainable fishing:

• Fishing quotas limit the number of fish caught to sustainable levels
• Minimum net mesh sizes allow young fish to escape and mature
• Restrictions on fishing during breeding seasons protect populations
• Fish farming (aquaculture) reduces pressure on wild stocks, though it has its own environmental concerns

Ecotourism:

• Tourism that minimises environmental impact and benefits local communities
• Generates income that funds conservation efforts
• Educates visitors about conservation issues
• Example: gorilla tourism in Rwanda provides income while protecting gorilla habitat

Recycling and reducing consumption:

• Reduces demand for raw materials, decreasing habitat destruction from mining and logging
• Reduces pollution from waste disposal
• Saves energy compared to producing new materials
• Particularly important for metals, paper and plastics

Alternative energy sources:

• Renewable energy (solar, wind, hydroelectric) reduces reliance on fossil fuels
• Decreases greenhouse gas emissions contributing to climate change
• Biomass fuels can be sustainable if crops are replanted
• However, large-scale hydroelectric and biomass projects can themselves destroy habitats

Education and raising awareness

Public understanding and support are essential for conservation success:

Education programmes:

• Schools teach students about biodiversity and conservation
• Zoos and museums provide educational resources and experiences
• Media coverage raises awareness of conservation issues
• Scientific research improves understanding of species' needs

Community involvement:

• Local communities managing their own resources often achieve better conservation outcomes
• Indigenous knowledge can inform conservation strategies
• Economic benefits from conservation (e.g., ecotourism jobs) increase local support
• Volunteer programmes engage citizens in conservation activities

Worked examples

Example 1: Explaining the importance of biodiversity

Question: Explain why maintaining high biodiversity is important for humans. [4 marks]

Model answer:

• High biodiversity provides many species that can be used for food [1]
• Many medicines are derived from plants and animals found in biodiverse ecosystems [1]
• Ecosystems with high biodiversity are more stable, which maintains ecosystem services like pollination and nutrient cycling [1]
• Biodiversity has economic value through industries such as tourism, which generates income [1]

Examiner note: This question requires four separate points. Each point should identify a specific benefit. Avoid vague statements; be precise about how biodiversity benefits humans.

Example 2: Comparing conservation methods

Question: Compare the advantages and disadvantages of conserving endangered species through captive breeding programmes compared to protecting them in nature reserves. [6 marks]

Model answer:

Captive breeding advantages:

• Animals are protected from predators and poaching, increasing survival rates [1]
• Breeding can be carefully controlled to maximise genetic diversity [1]
• Veterinary care ensures good health and increases reproductive success [1]

Captive breeding disadvantages:

• Animals may lose natural behaviours needed for survival in the wild [1]
• Expensive to maintain facilities and provide specialist care [1]
• Limited space means only small populations can be kept [1]

Nature reserves advantages:

• Animals remain in natural habitat and maintain natural behaviours [1]
• Can protect entire ecosystems and all species within them [1]
• Less expensive than maintaining captive populations [1]

Nature reserves disadvantages:

• Animals still vulnerable to poaching and predation [1]
• Natural disasters or disease outbreaks can affect entire populations [1]
• Requires large areas of land [1]

Examiner note: For compare questions, ensure you address both methods. Aim for at least three points about each method (or two advantages and two disadvantages for each). Any 6 valid points from the list above would gain full marks.

Example 3: Sustainable development application

Question: A tropical country wants to develop its economy by increasing timber exports, but scientists are concerned about biodiversity loss. Suggest how the country could develop sustainably. [5 marks]

Model answer:

• Use selective logging, removing only mature trees rather than clear-cutting entire areas [1]
• This maintains forest structure and habitat for most species [1]
• Replant trees after logging to ensure forest regeneration [1]
• Establish protected areas where no logging is permitted to preserve biodiversity [1]
• Use certification schemes to gain better prices for sustainably sourced timber, increasing economic benefits [1]

Examiner note: Questions about sustainable development require you to balance economic needs with environmental protection. Explain both what to do and why it helps.

Common mistakes and how to avoid them

• Confusing conservation with preservation: Conservation involves active management and sustainable use, not simply leaving everything untouched. Always explain the specific actions taken, such as controlling grazing or removing invasive species.

• Vague statements about biodiversity importance: Avoid saying biodiversity is "important for the environment" without explaining why. Be specific: name the benefit (e.g., medicines, food, ecosystem stability) and explain how it helps humans or ecosystems.

• Mixing up causes of biodiversity loss: Students often write generally about "pollution" or "habitat loss" without detail. Specify the type (e.g., eutrophication from fertiliser runoff) and explain how it reduces biodiversity.

• Forgetting both sides of sustainability questions: When asked about sustainable development, you must address both economic/social needs AND environmental protection. One without the other is not sustainable.

• Insufficient detail on conservation methods: Don't just name a method (e.g., "use seed banks"); explain how it works and why it conserves biodiversity. For captive breeding, mention increasing population numbers and genetic management; for seed banks, mention long-term storage and potential for restoration.

• Ignoring command words: "Explain" requires reasons or mechanisms, "describe" requires characteristics or steps, "suggest" requires applying knowledge to new contexts. Tailor your answer structure to the command word used.

Exam technique for "Conservation of biodiversity"

• Identify the command word first: "Explain" questions require you to give reasons (use "because," "this causes," "as a result"). "Describe" questions need factual statements without explanation. "Suggest" questions require you to apply knowledge to unfamiliar situations.

• Match the number of marks to points made: For a 4-mark question, aim for four distinct points. If a mark scheme shows [2], provide two separate ideas or one idea with development (e.g., name a method plus explain how it works).

• Use correct terminology consistently: Use specification terms like "captive breeding programme," "sustainable development," "habitat destruction," rather than informal language. This demonstrates precise understanding and earns marks.

• Structure longer answers clearly: For 6-mark questions, consider organising your answer with subheadings or clear paragraphs (e.g., "Methods used:" followed by bullet points). This ensures you cover all aspects and don't miss marks through poor organisation.

Quick revision summary

Biodiversity—the variety of species on Earth—provides essential benefits including food, medicines, ecosystem stability and economic value. Major threats include habitat destruction, climate change, pollution, overhunting and invasive species. Conservation methods protect endangered species through legal protection, captive breeding, and seed banks. Habitat conservation uses nature reserves, restoration and sustainable management. Sustainable development balances human needs with environmental protection through sustainable forestry, fishing quotas, ecotourism and renewable energy. Education and community involvement support long-term conservation success.