Conservation Biology, Restoration, and Sustainable Practice
Conservation biology is the scientific study of the protection of biodiversity, restoration ecology is the repair of damaged ecosystems, and sustainable practice means using resources in a way that meets present needs without reducing the ability of future generations to meet theirs. In brief: conservation works at the level of genes, species and ecosystems, using protected areas, captive breeding, laws and community involvement. Extinction risk is assessed with the IUCN Red List, and the effective size of a population is usually smaller than the number of individuals, which matters for inbreeding.
The current rate of extinction is estimated to be tens to hundreds of times higher than the average over the last tens of millions of years, and over a million species are thought to be threatened according to a 2019 IPBES assessment. This guide explains the aims and methods of conservation, restoration and sustainable use, compares in-situ and ex-situ conservation in a table, works through a calculation of inbreeding and population viability, and corrects common mistakes.
What does conservation biology aim to do?
Conservation biology aims to protect three levels of biodiversity: genetic diversity within species, species diversity, and ecosystem diversity. It uses ecology, genetics and social science. Reasons for conservation include the ecosystem services that nature provides (pollination, clean water, flood control, carbon storage), direct use (food, medicine, materials), cultural and aesthetic values, and the view that species have an intrinsic right to exist.
The main threats are summarized by the acronym HIPPO: Habitat destruction, Invasive species, Pollution, Population growth (human consumption) and Overharvesting, with climate change as an increasing threat. The IUCN Red List classifies species in categories such as Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild and Extinct, using criteria such as population decline, range size and population size.
How are species protected in nature?
In-situ conservation protects species in their natural habitat.
- Protected areas: national parks, nature reserves and marine protected areas. The Kunming-Montreal Global Biodiversity Framework (2022) set a target to protect 30 percent of land and sea by 2030 (“30 by 30”). Reserves work better if they are large, connected by corridors, and have community support and enforcement (“paper parks” exist on maps only).
- Laws and agreements: CITES regulates international trade in endangered species, and national acts such as the US Endangered Species Act (1973) protect species and habitat.
- Managing threats: removing invasive predators from islands (rats on South Georgia and others), anti-poaching patrols, and sustainable fishing quotas.
- Community-based conservation: involving local people so that they benefit, for example from ecotourism or shared management of wildlife, as in conservancies in Namibia.
- Reintroduction: returning species to areas where they have been lost, such as wolves to Yellowstone in 1995 and 1996, or the Arabian oryx to Oman.
How are species protected outside nature?
Ex-situ conservation protects species outside their habitat: in zoos, aquariums, botanic gardens, seed banks and cryopreservation of gametes and tissues. Examples include captive breeding of the California condor (population of 22 birds in the 1980s, now several hundred, with more than half living in the wild), the black-footed ferret, and the Svalbard Global Seed Vault, which stores duplicates of seed samples from gene banks around the world. Studbooks are used to manage matings in captivity so as to keep genetic diversity.
In-situ and ex-situ conservation compared
| Feature | In-situ | Ex-situ |
|---|---|---|
| Location | Natural habitat | Zoos, gardens, seed banks |
| Protects | Species and the ecosystem, with natural evolution | Individuals and genes |
| Advantages | Maintains ecological interactions | Safe from threats, allows breeding and research |
| Limits | Threats may continue | Limited space, loss of wild behavior, adaptation to captivity |
| Example | National park, marine reserve | Captive breeding, seed vault |
What is restoration ecology?
Restoration is the process of assisting the recovery of an ecosystem that has been degraded or destroyed. The aim is a self-sustaining ecosystem that resembles the original in species and function, though this may not be fully achievable. Approaches include:
- Bioremediation: using organisms such as bacteria to clean up pollution, for example oil.
- Reforestation and revegetation: planting native species, with attention to the diversity and not only to the number of trees.
- Restoring hydrology: removing dams, re-wetting peatlands and re-establishing wetlands and mangroves.
- Rewilding: the reintroduction of key species, such as large herbivores and predators, to restore ecological processes. Keystone species are sometimes the focus. Beavers help to create wetlands.
- Controlling invasive species and restoring natural fire regimes.
- Succession: restoration works with natural succession, and sometimes the best action is to remove the cause of damage and wait.
The UN Decade on Ecosystem Restoration (2021 to 2030) aims to scale up restoration. Restoration is costly and slow, so preventing damage is usually cheaper and more effective.
What are sustainable practices?
The Brundtland Report (1987) defined sustainable development as development that meets the needs of the present without compromising the ability of future generations to meet their own needs. It rests on three dimensions: environmental, social and economic. Examples:
- Sustainable agriculture: crop rotation, cover crops, integrated pest management, reduced tillage, agroforestry and efficient irrigation.
- Sustainable fishing and forestry: harvest below the maximum sustainable yield, size limits and closed seasons, and certification such as MSC and FSC.
- Renewable energy and efficiency to cut emissions.
- Circular economy: reduce, reuse, repair and recycle, so that waste is minimized.
- Individual choices: reducing food waste, using public transport, and choosing products that have less impact.
Worked example: small populations and inbreeding
A captive population of an endangered species has 20 breeding adults: 4 males and 16 females. Because the sex ratio is unequal, the effective population size (Ne) is less than 20.
- Formula for unequal sex ratio: Ne = (4 × Nm × Nf) ÷ (Nm + Nf).
- Substitute: Ne = (4 × 4 × 16) ÷ (4 + 16) = 256 ÷ 20 = 12.8.
- Loss of heterozygosity per generation: approximately 1 ÷ (2Ne) = 1 ÷ 25.6 = 0.039, or about 3.9 percent per generation.
- Improved management: with 10 males and 10 females, Ne = (4 × 10 × 10) ÷ 20 = 20, and the loss is 1 ÷ 40 = 2.5 percent per generation.
Equalizing the sex ratio reduces the rate of loss of genetic diversity without increasing the number of animals. A rule of thumb sometimes used in conservation genetics is that an Ne of 50 is needed to avoid the short-term effects of inbreeding, and 500 to keep long-term evolutionary potential (the “50/500 rule”, which has been revised upward in recent studies). The real effective size is also reduced by variation in family size and fluctuations in numbers.
How did conservation develop?
The first national park, Yellowstone, was established in 1872. Aldo Leopold’s A Sand County Almanac (1949) set out a “land ethic”. The IUCN was founded in 1948, and the Red List started in 1964. CITES entered into force in 1975. Michael Soulé is regarded as a founder of conservation biology as a discipline, with the Society for Conservation Biology established in 1985. The Convention on Biological Diversity was signed at the Rio Earth Summit in 1992, and the Kunming-Montreal Framework was adopted in 2022.
Which mistakes are common?
Mistake 1: Equating conservation with preservation
Conservation often includes wise use and management. Preservation means keeping nature untouched.
Mistake 2: Assuming that captive breeding alone saves a species
It is a tool, not a solution. Threats in the wild must also be dealt with, or the animals cannot be released.
Mistake 3: Counting individuals instead of effective population size
A population with unequal sex ratio or few breeders loses genetic diversity faster than its size suggests.
Mistake 4: Thinking that restoration can fully replace what was lost
Restored ecosystems often differ from the originals and need decades to develop. Protection of intact habitat is more effective.