Conservation Biology: Biodiversity, Extinction and Recovery

Conservation biology is the applied science of protecting biodiversity. It emerged as a discipline in the 1980s, when the ecologist Michael Soulé described it as a “crisis discipline”: like emergency medicine, it has to act on the best evidence available, often before all the facts are known. It draws on ecology, genetics, economics, social science and law.

What you will learn

• The three levels of biodiversity and why biodiversity matters
• How the IUCN Red List categorises extinction risk
• The five main drivers of biodiversity loss
• The main conservation tools, from protected areas to reintroductions
• The role of people, communities and health in conservation

What is biodiversity?

Biodiversity is the variety of life at three levels:

1. Genetic diversity: the variation of genes within a species. It allows populations to adapt to disease and environmental change.
2. Species diversity: the variety of species. About 2.2 million species have been formally described, but estimates of the total range from about 8 million to many more, most of them insects, fungi and microorganisms.
3. Ecosystem diversity: the variety of habitats and ecological processes, from coral reefs to tundra.

Biodiversity is not evenly spread. Thirty-six biodiversity hotspots identified by Conservation International cover about 2.5 percent of Earth’s land but hold more than half of all plant species as endemics.

Why biodiversity matters

• Ecosystem services: pollination, clean water, fertile soil, climate regulation, flood protection and fisheries (see Module 14).
• Resilience: diverse ecosystems tend to be more stable and recover faster from disturbance.
• Medicine and food: many medicines come from natural compounds, and wild relatives of crops provide genes for disease resistance.
• Culture and well-being: nature is central to identity, spirituality and recreation for people everywhere.
• Intrinsic value: many people believe species have a right to exist regardless of their use to humans.

Measuring extinction risk: the IUCN Red List

The IUCN Red List of Threatened Species, maintained by the International Union for Conservation of Nature since 1964, is the world’s most comprehensive assessment of extinction risk. Species are assessed against quantitative criteria based on population size, rate of decline, geographic range and the probability of extinction.

CR, EN and VU are together called threatened. More than 46,000 species on the Red List are threatened, including about 41 percent of amphibians, over a quarter of mammals and over a third of reef-building corals.

The drivers of biodiversity loss

The global assessment by IPBES (the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) in 2019 identified five main direct drivers, in approximate order of global impact:

1. Changes in land and sea use, especially conversion of forests, grasslands and wetlands to agriculture.
2. Direct exploitation of organisms through hunting, fishing, logging and wildlife trade.
3. Climate change (see Module 12).
4. Pollution, including pesticides, fertilisers, plastics and light and noise.
5. Invasive alien species, which have contributed to many recorded extinctions, especially on islands.

The report estimated that around one million species face extinction, many within decades, unless action is taken. These drivers are themselves driven by indirect factors: consumption, population, trade, technology and governance.

Small populations and the extinction vortex

Once a population becomes small, it faces additional risks that can pull it into an extinction vortex:

• Inbreeding, which reduces fitness and exposes harmful genes.
• Loss of genetic diversity through genetic drift, reducing the ability to adapt.
• Demographic chance, such as a run of male-only births.
• Environmental catastrophes, such as a single disease outbreak or storm.

The Florida panther shows both the problem and a solution. By the 1990s, about 20 to 30 panthers survived, with kinked tails, heart defects and poor sperm quality caused by inbreeding. In 1995, eight female pumas from Texas were released to bring in new genes, a technique called genetic rescue. The population has since grown to around 200.

Conservation tools

Protected areas

National parks, reserves and marine protected areas are the cornerstone of conservation. About 17 percent of land and 8 percent of the ocean are now in protected areas. In 2022, under the Kunming-Montreal Global Biodiversity Framework, almost 200 countries agreed to protect 30 percent of land and sea by 2030 (known as 30×30) and to restore 30 percent of degraded ecosystems. What matters is not just the area protected but how well it is managed and connected.

Species recovery and reintroduction

• Captive breeding and reintroduction has saved species such as the Arabian oryx, Przewalski’s horse, the California condor and the black-footed ferret.
• Translocation moves wild animals to establish new populations, such as black rhinos moved to Rwanda’s Akagera and Malawi’s Liwonde.
• Rewilding restores natural processes, often by returning large animals such as bison, beavers and wolves.

Tackling wildlife trade

CITES, the Convention on International Trade in Endangered Species (in force since 1975), regulates international trade in more than 40,000 species. Enforcement, reducing demand and supporting rangers are all needed to stop illegal trade.

Community-based conservation

Conservation works best when local people benefit. Examples include Namibia’s communal conservancies, Nepal’s community forests and buffer-zone programmes, and gorilla tourism in Rwanda and Uganda, where a share of permit revenue goes to local communities. Indigenous peoples manage or have rights over a quarter of the world’s land, which overlaps with a large share of its intact ecosystems.

Financing conservation

Tools include ecotourism, payments for ecosystem services, debt-for-nature swaps, biodiversity credits and conservation trust funds. Ecotourism can be powerful but is vulnerable to shocks, as the COVID-19 pandemic showed.

One Health

One Health recognises that the health of people, animals and ecosystems is connected. About 60 percent of known infectious diseases in people are zoonotic, meaning they originated in animals, including Ebola, HIV and avian influenza. Habitat destruction, wildlife trade and intensive livestock farming increase contact between wildlife, livestock and people, raising the risk of new diseases emerging. Conserving ecosystems is therefore also a public health strategy.

Case study: bringing back the mountain gorilla

In the early 1980s, only about 250 mountain gorillas survived in the Virunga Volcanoes. The combination of strict protection, veterinary care, anti-poaching patrols and carefully managed tourism, which gives local communities and governments a strong financial reason to protect gorillas, reversed the decline. By 2018 the population had passed 1,000, and the IUCN moved the mountain gorilla from Critically Endangered to Endangered. The success came despite civil war, poverty and one of the densest human populations in Africa surrounding the parks.

Try it yourself

Choose a threatened species and look up its IUCN Red List assessment online. What category is it in? Which criteria were used? What are its main threats, and what conservation actions are recommended?

Common misconceptions

• “Extinction is natural, so we shouldn’t worry.” Background extinction happens, but current rates are estimated to be tens to hundreds of times higher than the average over the past 10 million years.
• “Conservation means keeping people out.” Many of the most successful projects involve and benefit local communities.
• “Zoos have no role in conservation.” Well-run zoos contribute to breeding programmes, research and education, although protecting habitat is always the priority.

Key terms

• Biodiversity: the variety of life at genetic, species and ecosystem levels.
• Endemic species: a species found only in one place.
• Threatened: IUCN categories CR, EN and VU combined.
• Extinction vortex: the downward spiral of small populations.
• Genetic rescue: introducing new individuals to restore genetic diversity.
• One Health: the connected health of people, animals and ecosystems.

Quick quiz

Test what you have learned. Scoring 60 percent or more marks this module as complete.

Further reading

• IPBES (2019). Global Assessment Report on Biodiversity and Ecosystem Services.
• Primack, R. B. Essentials of Conservation Biology.