Have you ever been to the zoo? If you have, you've witnessed ex-situ conservation in action. Around the world, thousands of threatened animals are removed from their natural habitat to keep the species alive and maintain their genetic diversity. But it's not just animals – plants can be conserved ex-situ in botanical gardens or seed banks. Read on to find out more about ex-situ conservation and why it's needed!
- This article is about Ex-situ conservation.
- We’ll start with the definition of ex-situ conservation, contrasting it with in-situ conservation.
- Then, we’ll learn the uses of ex-situ conservation, when and how it can be used.
- We’ll continue with the description of ex-situ conservation strategies, for both animals and plants.
- We’ll also see some examples of ex-situ conservation.
- We’ll finish comparing some disadvantages and benefits of ex-situ conservation.
Ex-situ Conservation: Definition
First things first, what is ex-situ conservation?
Ex-situ conservation is the conservation of biodiversity outside its natural habitats.
'Ex-situ' is Latin for 'out of place'.
Ex-situ vs In-situ
Ex-situ conservation takes place outside natural habitats. In contrast, in-situ conservation takes place within a species' natural habitat. In-situ conservation is often preferred and prioritised. This is because it helps preserve recovering populations in their natural habitat, with minimal disturbance. This strategy helps to create and maintain conditions for species adaptation within their environment. As a result, ex-situ conservation is only used as a last resort or complementary to in-situ strategies.
Uses of Ex-situ Conservation
The uses of ex-situ conservation techniques focus on ensuring the survival of threatened species and maintaining their genetic diversity.
Why Do We Need Ex-situ Conservation?
More than 41,000 species of animal and plant are threatened with extinction around the world.
Threats to biodiversity include:
With so many species at risk, how do scientists decide which species are most in need of ex-situ conservation?
Criteria for Species Selection
Typically, ex-situ conservation focuses on charismatic, rare, or agricultural species.
Charismatic species are usually animals that possess something people see to be attractive such as intelligence, beauty and cuteness.
There is a significant taxonomic bias within animal ex-situ conservation: 41% of the world's amphibians are under threat, but only 3% are in zoos. Zoos are biased towards mammals; they achieve the most attention and concern from the public.
To decide if ex-situ conservation is appropriate, ecologists must use a five-step decision-making tool.
What is the extinction risk of the species?
Can ex-situ management play a positive role?
What characteristics and dimensions does the ex-situ population need to meet its conservation goal?
What resources and expertise are needed?
Is ex-situ conservation suitable for this species?
Extinction Risk
The IUCN Red List determines and classifies species according to their extinction risk. The nine categories are:
- Not Evaluated (NE)
- Data Deficient (DD)
- Least Concern (LC)
- Near Threatened (NT)
- Vulnerable (VU)
- Endangered (EN)
- Critically Endangered (CR)
- Extinct in the Wild (EW)
- Extinct (EX)
Ex-situ Conservation Strategies
Ex-situ conservation strategies vary depending on the target species. They are used for animals and plants – but it's a lot easier to maintain plants than animals!
Animals
Living animals are kept in ex-situ collections such as zoos and aquariums to keep them alive and maintain their genetic diversity. Over 700 million people visit zoos every year.
Fig. 1: Zoos keep many species out of harm's way. Source: Unsplash.
How do zoos help conserve a threatened animal species?
Captive Breeding Programmes
These programmes aim to increase the number of individuals of a species if the population is very small. Scientists try to maximise genetic diversity within the captive population by using studbooks.
Studbooks keep track of the history and location of all captive animals in the breeding plan.
Using studbooks aims to ensure an equal representation of genes. Poor breeders are encouraged to breed, whilst particularly good breeders may be limited. In the future, the captive breeding population may be reintroduced to the wild.
Reintroducing captive populations into the wild isn't as easy as it sounds. If animals have been kept in captivity for too long, it can be difficult to reconnect with others in the habitat.
Behavioural changes may have also taken place during captivity. In a zoo, animals don't have to search for their food or deal with predators and similar hazards. When reintroduced to the wild, they lack survival instinct and may die of hunger or predation. Thus, animals require preconditioning before they are released back into their natural habitat.
Tasmanian devil populations were decimated by a transmissible facial tumour disease. To combat the disease, scientists established captive populations free from the disease. However, devils that were then reintroduced to Tasmania suffered unusually high rates of fatal vehicle strikes. The more generations the devils had been in captivity, the more naive they were to wild conditions, thus the more likely they were to be hit by a car.
Plants
Ex-situ plant conservation usually takes place in the form of a seed bank. These artificial yet valuable hotspots of biodiversity store millions of seeds as an insurance against extinction, and to maintain genetic diversity.
The Millennium Seed Bank is the UK's largest seed bank. This Sussex-based collection is home to over 2.4 billion seeds, from almost 40,000 plant species. The seeds are dried and then stored at -20 °C. After a few weeks, the samples are germinated to ensure their survival and then tested every decade.
As well as seed banks, plants can be kept in botanical gardens.
Fig. 2: Greenhouses are often used in botanical gardens to simulate a warmer habitat. Source: Unsplash.
Examples of Ex-situ Conservation
Ex-situ conservation has been successful at keeping species alive.
Back from the Brink
A famous example of captive breeding success is the black-footed ferret, North America's only resident ferret species. They frequently eat rodents, but prairie dogs constitute the majority of their diet.
Prairie dogs are herbivorous burrowing ground squirrels.
Unfortunately, many prairie dog populations were eliminated because they caused damage to agricultural fields. As a result, the black-footed ferret experienced a severe decline. In 1987, eighteen ferrets were used to start a captive breeding programme, which has successfully introduced black-footed ferrets back into the wild. However, they remain endangered.
Fig. 3: Since the 1990s, almost 4000 kits have been released back into the wild.
Extinct in the Wild
The Alagoas curassow is a pheasant-like bird found in northeastern Brazil. It is extinct in the wild; all 130 members of the species live in captivity. Little was known about the birds before captivity, as they were seldom seen by scientists. Reintroducing the birds to their natural habitat will be tricky. Most surviving individuals have been hybridised with another curassow species. True Alagoas curassows have limited genetic diversity.
Drawbacks and Benefits of Ex-situ Conservation
The pros and cons of ex-situ conservation depend on the species being conserved.
Animals
| Benefits | Drawbacks |
- Animals are kept safe from external threats (such as predators and poachers) in a controlled environment, with all their needs provided
- Zoos are an invaluable resource for research: they provide a greater understanding of animals' needs. Scientists can also carry out studies difficult to do in wild populations
- Zoos educate the public about endangered species and conservation efforts
- It has the potential to reintroduce organisms back into their natural habitat
| - Captive breeding can reduce genetic diversity. Furthermore, not all species will breed in captivity
- Ex-situ conservation is not applicable to all species; it can be difficult to provide an adequate habitat
- Maintaining animal populations is incredibly expensive
- Behavioural issues: animals suffer from boredom, stress, aggression, and other behavioural problems
- Interbreeding and hybridisation often take place
- The artificial environment is not as suitable as the animals' natural habitat
|
Table 1: Common benefits and drawbacks of animal
ex-situ conservation.
Plants
| Benefits | Drawbacks |
- Seeds can be stored anywhere in the world
- Seed banks have low labour requirements
- Millions of seeds can be stored per bank because they take up little space
- Less vulnerable to disease, natural disaster and human destruction outside the natural habitat
- Visitors to botanical gardens bring in money
| - Expensive and time-consuming to test the viability of seeds
- Not always possible to store and test all seeds – it can be challenging to collect seeds from plants growing in remote habitats
- Disease can easily spread in botanical gardens
- Botanical gardens can be expensive to run
|
Table 2: Common benefits and drawbacks of plant ex-situ conservation.Conserving plants via ex-situ techniques is easier and less disruptive to the species, thus has fewer drawbacks than ex-situ animal conservation.
I hope that this article has clarified ex-situ conservation for you. It's a type of conservation where threatened species are taken out of their natural habitat to be stored or looked after elsewhere. The controlled conditions keep the species safe and provide an invaluable research opportunity, but the artificial environment can affect behaviour and genetic diversity.
Ex-situ conservation - Key takeaways
- Ex-situ conservation is the conservation of biodiversity outside its natural habitats. It is used as a last resort if in-situ conservation has been unsuccessful.
- Over 41,000 species around the world are facing the risk of extinction. Scientists follow a specific set of criteria to determine if ex-situ conservation is suitable to protect these species. Charismatic, rare, and agricultural species are prioritised.
- Animals are kept in zoos are aquaria to provide a safe environment and research opportunities. Captive breeding programmes often take place in zoos. Plants are kept in seed banks or botanical gardens.
- Ex-situ conservation keeps animals and plants safe from external threats and educates the public about conservation efforts. However, ex-situ conservation is expensive and can impact the behaviour and genetic diversity of animals in captivity.
1. D. Conde, An Emerging Role of Zoos to Conserve Biodiversity, Science, 2011
2. Field Studies Council, Ex-situ conservation management, 2022
3. IUCN, IUCN Red List of Threatened Species, 2022
4. Meryl Westlake, 20 facts to celebrate 20 years of the Millennium Seed Bank, Kew, 2020
5. National Geographic, Black-Footed Ferret, 2022
6. University of Sydney, Captive-bred Tasmanian devils susceptible to car strike, 2017
References
- Fig. 1: Giraffes and zebras in the zoo (https://unsplash.com/photos/ttpNCevA1tA) by Nikolay Tchaouchev, free to use under the Unsplash License (https://unsplash.com/license).
- Fig. 2: Botanic garden (https://unsplash.com/photos/kEcrRoxMnBY) by Toa Hertiba, free to use under the Unsplash License (https://unsplash.com/license).
- Fig. 3: Black footed ferret (https://commons.wikimedia.org/wiki/File:Black_footed_ferret_picture.jpg) by Ryan Hagerty, Public domain.
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