A4.

2 Conservation of biodiversity Both levels (No HL) Guiding questions

• What factors are causing the sixth mass extinction of species?
• How can conservationists minimize the loss of biodiversity?
A4.2.1—Biodiversity as the variety of life in all its forms, levels and combinations
Include ecosystem diversity, species diversity and genetic diversity.
A4.2.2—Comparisons between current number of species on Earth and past levels of biodiversity
Millions of species have been discovered, named and described but there are many more species to be discovered. Evidence from
fossils suggests that there are currently more species alive on Earth today than at any time in the past.
NOS: Classification is an example of pattern recognition but the same observations can be classified in different ways. For example,
“splitters” recognize more species than “lumpers” in a taxonomic group.
A4.2.3—Causes of anthropogenic species extinction
This should be a study of the causes of the current sixth mass extinction, rather than of non-anthropogenic causes of previous mass
extinctions.
To give a range of causes, carry out three or more brief case studies of species extinction: North Island giant moas (Dinornis
novaezealandiae) as an example of the loss of terrestrial megafauna, Caribbean monk seals (Neomonachus tropicalis) as an
example of the loss of a marine species, and one other species that has gone extinct from an area that is familiar to students.
Note: When students are referring to organisms in an examination, either the common name or the scientific name is acceptable.
A4.2.4—Causes of ecosystem loss
Students should study only causes that are directly or indirectly anthropogenic. Include two case studies of ecosystem loss. One
should be the loss of mixed dipterocarp forest in Southeast Asia, and the other should, if possible, be of a lost ecosystem from an
area that is familiar to students.
A4.2.5—Evidence for a biodiversity crisis
Evidence can be drawn from Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services reports and other
sources. Results from reliable surveys of biodiversity in a wide range of habitats around the world are required. Students should
understand that surveys need to be repeated to provide evidence of change in species richness and evenness. Note that there are
opportunities for contributions from both expert scientists and citizen scientists.
NOS: To be verifiable, evidence usually has to come from a published source, which has been peerreviewed and allows
methodology to be checked. Data recorded by citizens rather than scientists brings not only benefits but also unique methodological
concerns.
A4.2.6—Causes of the current biodiversity crisis
Include human population growth as an overarching cause, together with these specific causes: hunting and other forms of over-
exploitation; urbanization; deforestation and clearance of land for agriculture with consequent loss of natural habitat; pollution and
spread of pests, diseases and invasive alien species due to global transport.
A4.2.7—Need for several approaches to conservation of biodiversity
No single approach by itself is sufficient, and different species require different measures. Include in situ conservation of species in
natural habitats, management of nature reserves, rewilding and reclamation of degraded ecosystems, ex situ conservation in zoos
and botanic gardens and storage of germ plasm in seed or tissue banks.
A4.2.8—Selection of evolutionarily distinct and globally endangered species for conservation prioritization in the EDGE of Existence
programme
Students should understand the rationale behind focusing conservation efforts on evolutionarily distinct and globally endangered
species (EDGE).
NOS: Issues such as which species should be prioritized for conservation efforts have complex ethical, environmental, political,
social, cultural and economic implications and therefore need to be debated.
A4.2.1—Biodiversity as the variety of life in all its forms, levels and combinations
Include ecosystem diversity, species diversity and genetic diversity.

l Ecosystem diversity is the range of different habitats or number of ecological niches per unit area in an
ecosystem. For example, a woodland may contain many different habitats (e.g. river, soil, trees) and so have a
high ecosystem diversity, whereas a desert has few (e.g. sand, occasional vegetation) and so has a low diversity.
Conservation of ecosystem diversity usually leads to the conservation of species and genetic diversity.
l Species diversity is the variety of species per unit area. This includes both the number of species present and
their relative abundance.
l Genetic diversity is the range of genetic material present in a gene pool or population of a species. A large gene
pool leads to high genetic diversity and a small gene pool to low genetic diversity. Although the term normally
refers to the diversity within one species, it can also be used to refer to the diversity of genes in all species within
an area.
A4.2.2—Comparisons between current number of species on Earth and past levels of biodiversity
Millions of species have been discovered, named and described but there are many more species to be discovered.
Evidence from fossils suggests that there are currently more species alive on Earth today than at any time in the past.
NOS: Classification is an example of pattern recognition but the same observations can be classified in different ways.
For example, “splitters” recognize more species than “lumpers” in a taxonomic group.

Scientists do not know how many different types of organisms exist. Millions of species have been discovered, named and
described, but there are many more species to be discovered. Estimates of the number of species on Earth range from 5 to 100
million, with the scientific consensus currently being around 9 million species. This estimate is broken down as follows:
l animals: 7.77 million (12% of which are described)
l fungi: 0.61 million (7% of which are described)
l plants: 0.30 million (70% of which are described)
l other species: 0.07 million.

Relative levels of genera in the past using fossil evidence

A4.2.3—Causes of anthropogenic species extinction
This should be a study of the causes of the current sixth mass extinction, rather than of non-anthropogenic causes of previous mass extinctions.
To give a range of causes, carry out three or more brief case studies of species extinction: North Island giant moas (Dinornis novaezealandiae)
as an example of the loss of terrestrial megafauna, Caribbean monk seals (Neomonachus tropicalis) as an example of the loss of a marine species,
and one other species that has gone extinct from an area that is familiar to students.
Note: When students are referring to organisms in an examination, either the common name or the scientific name is acceptable

Case study 1: North Island giant moas

The North Island giant moa (Dinornis novaezealandiae) is one of three extinct moa in the genus
Dinornis that were endemic to New Zealand They were a group of flightless birds and were the second tallest of the nine moa species,
measuring up to 2 metres from the ground to their back and up to 3 metres tall including their necks. The North Island giant moa
also showed sexual dimorphism (differences between females and males) with adult females being much larger than adult males.
This species of moa lived on New Zealand’s North Island in the lowlands, shrublands, grasslands,
dune lands and forests. It is an example of terrestrial megafauna, which are the large or giant animals
of an area, habitat or geological period, extinct and/or extant (living). The population size of the giant moa
remained stable over the past 40 000 years until the arrival of humans, the Maori, in New Zealand around 1280.

The giant moa, along with other moa genera, were hunted for food. All taxa in this genus were extinct by 1500 in New Zealand.
The most important contributing
factor was probably farming, however, since the forests were cut and burned down and the ground was turned into arable land.
Studies of ancient DNA from the bones of giant extinct New Zealand birds demonstrate that significant climate and geological
environmental changes did not have a major impact on their populations. Ancient DNA, radiocarbon dating and stable dietary isotope
analysis have shown that, before humans arrived,
moa adapted to the effects of climate change on their species by tracking their preferred habitat as it expanded, contracted and shifted
during warming and cooling events.
Moa were very large and as so played a major role in shaping the structure and composition of vegetation communities.
The extinction of moa could have affected New Zealand’s ecosystems through altering vegetation composition and structure,
regeneration patterns and fire frequency.
Case study 2: Caribbean monk seals
The Caribbean monk seal (Neomonachus tropicalis) was declared extinct in 2008 and is an example of
the loss of a marine species. At their peak abundance, this species had a widespread
distribution throughout the Caribbean Sea, Gulf of Mexico and western Atlantic Ocean, and their
habitat included areas around the east coast of Central America and north coast of South America.
The Caribbean monk seal was part of a group called Pinnipedia (pinnipeds), which includes sea
lions and walruses. They are the only pinniped species to have become extinct. Reasons for the
seal’s extinction included being hunted for fur and meat, and oil from its blubber; being captured
for display in museums and zoos; and overfishing activities that disturbed their habitat and reduced
their prey species (mainly fish). They were easy to kill because of their tame and non-aggressive
behaviour, which meant that hunters could get close to them. NOAA (National Oceanic and
Atmospheric Administration) Fisheries has stated it was the first species of seal to become extinct
because of human causes.
The extinction of the monk seal had a huge knock-on effect across the Caribbean’s food web. The
monk seal was a top predator, feeding on a variety of fish and invertebrates, so its disappearance
allowed some species of fish to expand at the expense of others, significantly altering the biodiversity
of the areas where the seal had been found.
At one point there were an estimated 233 000–338 000 monk seals distributed among 13 colonies
across the Caribbean.
Such an extensive population could only survive because there was a large quantity of food
available: each adult seal would eat approximately 245 kg of fish per year. The loss of
historically dense monk seal colonies, and their consumption rates, severely impacted other species
in the Caribbean coral reefs.

Case study 3: Falkland Islands wolf

The Falkland Islands wolf was the only native land mammal of the Falkland Islands. These remote South Atlantic islands,
about 480 kilometres northeast of the southern tip of South America, were first sighted by Europeans in 1692. In 1833, Charles
Darwin visited the islands and described the wolf as ‘common and tame’.
The Falkland Islands wolf is said to have lived in burrows.
As there were no native rodents on the islands (the usual prey), it is probable that its diet consisted of ground-nesting birds
(such as geese and penguins), grubs, insects and some seashore scavenging.
The many settlers of the islands (mainly Scottish inhabitants but also some French and English) considered the Falkland
Islands wolf a threat to their sheep. A huge-scale operation of poisoning and shooting began with the aim of leading the wolf to
extinction. The operation was successful very rapidly, assisted by the lack of forests and the tameness of the animal (due to
the absence of predators the animal trusted humans, who would lure it with a piece of meat and then kill it).
The Falkland Islands wolf was not particularly threatening nor was it a significant predator, although the removal of a top
predator would have had an impact on the rest of the food chain, for example increasing the population size of its prey.
A4.2.4—Causes of ecosystem loss
Students should study only causes that are directly or indirectly anthropogenic. Include two case studies of ecosystem loss.
One should be the loss of mixed dipterocarp forest in Southeast Asia, and the other should, if possible, be of a lost ecosystem from an area
that is familiar to students.
An ecosystem is defined as a community of organisms and their surroundings, the environment in which they live and with which they interact. A
community (i.e. a group of different species living in an area) forms an ecosystem by its interactions with the abiotic (non-living) environment.
Disturbance and loss of ecosystems can be natural (for example, due to typhoons or volcanic activity), but currently is predominantly due to
anthropogenic causes.

Case study: The loss of mixed dipterocarp forests in

South East Asia
Tropical rainforests cover only 6% of the Earth’s land surface but may contain up to 50% of all species. They are found in South America, Africa, India,
South East Asia and Australia, close to the equator. The climate is warm and stable, with temperatures varying from 20 °C at night to 35 °C at midday,
and high rainfall, with up to 2500 mm per year. The constant warm temperatures, high insolation (sunlight) and high rainfall lead to high levels of
photosynthesis and high productivity.
High productivity leads to high amounts of biological matter and food, which in turn leads to ecosystem complexity, abundant resources (such as food)
and niche (the role an organism plays in its community) diversity. Abundant niches lead to high species richness and high biodiversity.
Tropical rainforests are vulnerable to disturbance. As they have high biodiversity, many species are affected when the rainforests are disturbed.
Deforestation and forest degradation are caused principally by demands for wood (Figure below), for land for cattle to provide beef, and for plantation
crops including soya and biofuels (such as palm oil in South East Asia). Tropical rainforests grow on nutrient-poor soils that are thin and easily eroded
once the forest has been cleared, which means that once forest is cleared and the soil eroded, it is difficult to re-establish a forest cover.
Dipterocarp trees are the main hardwood species in the tropical rainforests of South East Asia.
More than 270 species of dipterocarp trees have been identified so far in the island of Borneo, of which 155 are endemic.
In South East Asia, large areas of dipterocarp forest have been cleared to grow oil palms (Elaeis guineensis), see Figure A4.2.8. In Malaysia, for
example, 20% of land area is now covered by oil palm plantations, compared with 1% in 1974. Palm oil is used in food production (for example,
margarine, cooking oil, ice cream, ready meals, biscuits and cakes), domestic products such as detergents and cosmetics, and to provide biofuel. The
global production of palm oil exceeds 35 million tonnes
per year.

Once the original forest has been removed, natural nutrient recycling is also lost. As the soils are generally nutrient poor, oil palm trees require fertilizer to be
applied to produce yields that return reasonable profit. Fertilizers can have various negative environmental impacts. Fertilizer
application in oil palm plantations has also been linked to increases in ground-level ozone, which can have detrimental effects on both humans and wildlife,
and also reduces plant productivity.
The causes and effects of the loss of mixed dipterocarp forest in Borneo in South East Asia are summarized in the following table:
A4.2.5—Evidence for a biodiversity crisis
Evidence can be drawn from Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services reports and other sources.
Results from reliable surveys of biodiversity in a wide range of habitats around the world are required. Students should understand that surveys
need to be repeated to provide evidence of change in species richness and evenness. Note that there are opportunities for contributions from
both expert scientists and citizen scientists.
NOS: To be verifiable, evidence usually has to come from a published source, which has been peerreviewed and allows methodology to be
checked. Data recorded by citizens rather than scientists brings not only benefits but also unique methodological concerns.

Evidence for the current biodiversity crisis can be drawn from reports and other sources from the Intergovernmental Science-Policy Platform on
Biodiversity and Ecosystem Services (IPBES).
IPBES (https://ipbes.net) is an independent, intergovernmental body founded in 2012 by 94 countries to strengthen the link between scientific
information and policy decisions relating to conservation and the sustainable use of biodiversity, long-term human well-being and sustainable
development. Although it is not a United Nations (UN) organization, the United Nations Environment Programme (UNEP) provides help to IPBES.
Results from reliable surveys of biodiversity in a wide a range of habitats around the world are required to establish current levels of biodiversity and
to allow estimates of species extinction rates to be calculated. Such surveys may use the Simpson’s reciprocal index to compare communities
in undisturbed and disturbed habitats (see page 157 earlier this chapter). Surveys need to be repeated to provide evidence of change in species
richness and evenness. There are opportunities for contributions from both expert scientists and citizen scientists. Citizen science is scientific
research carried out, in whole or in part, by amateur (i.e. non-professional) scientists.
There are four common features of citizen science:
l anyone can participate
l participants use the same protocol so data can be combined and be high quality
l data can help professional scientists come to reliable conclusions
l a wide community of scientists and volunteers work together and share data to which the public, as well as scientists, have access.
Citizen science allows large quantities of data to be collected – more than would be possible by professional scientists alone. Given the scale and
imminent threats posed by the current biodiversity crisis, citizen science offers a rapid and global mechanism for gathering data that can be used to
support the conservation of species.
A4.2.6—Causes of the current biodiversity crisis
Include human population growth as an overarching cause, together with these specific causes: hunting and other forms of over-exploitation;
urbanization; deforestation and clearance of land for agriculture with consequent loss of natural habitat; pollution and spread of pests,
diseases and invasive alien species due to global transport.

Human population growth

For most of Earth’s history, natural processes have influenced and shaped life, such as plate tectonic movements, ocean and atmospheric currents, and
volcanic activity. More recently, one species – Homo sapiens – has been the dominant influence on Earth’s ecosystems. Early humans lived in balance
with nature, as hunter-gatherers, and had little impact on their environment. Populations were low in number and people lived off the land.
As humanity spread out from Africa, eventually becoming farmers and clearing land to grow crops, the impact of Homo sapiens on the planet grew. The
development of settled agriculture represents one of the most significant changes in human history and enabled human populations to start
growing. This period, known as the Neolithic (‘new stone age’) revolution, began in the ‘fertile crescent’ in the Middle East about 10 000 years ago, and
forever changed the way that humanity interacts with the environment.
In recent times, humanity’s tremendous growth in population, from around 2 million in the early Neolithic period to over 7 billion (7 × 109) today has put
even more pressure on the Earth’s natural systems.

Following the development of agriculture, human populations became settled in growing communities. Over the past 10 000 years, the domestication of
many species of plants and animals has occurred independently and in different ways in different parts of the world.
Production of staple foods enabled the human population to grow. During industrial revolutions, increased access to energy further fuelled population
growth. The world’s population doubled between 1804 and 1922, 1922 and 1959, 1959 and 1974. It is, therefore, taking less and less time for the
population to double. In the twentieth century, population growth became exponential (exponential means increasingly rapid growth).
Other factors have contributed to an increase in human population:
l better healthcare
l more nutritious food
l cleaner water
l better sanitation.
The biggest increase in population is in less economically developed countries (LEDCs) rather than in more economically developed countries (MEDCs).
High infant death rates increase the pressure on women to have more children, and in some agricultural societies parents have larger families to
provide labour for the farm and as security for the parents in old age. Lack of access to contraception, through education or medical services, also leads
to increased birth rates.
The impact of exponential growth is that enormous amounts of extra resources are needed to support growing populations (for food, housing and
clothing). Human population growth is an overarching cause of biodiversity loss, together with other specific causes such as hunting and other forms of
over-exploitation; urbanization; deforestation and clearance of land for agriculture with consequent loss of natural habitats; pollution and spread of pest
and diseases; and alien invasive species due to global transport.
■ Hunting and other forms of over-exploitation
Overharvesting and hunting have led to a significant reduction in population size of many species.
Animals are hunted for food, medicines, souvenirs, fashion and to supply the exotic pet trade.
Overharvesting of North Atlantic cod in the 1960s and 1970s led to significant reduction in
population numbers.
■ Urbanization
Today, some 4.2 billion (4.2 × 109) people (55% of the world’s population) live in cities. It is
predicted that by 2050, 68% of the world’s population will live in urban areas.
Urbanization refers to the increase in the proportion of people living in towns and cities. Living areas
are built on land that was once covered by natural habitats. For example, New York was built on land
that was a natural wetland environment: these areas were drained and filled in during the development
of the city. With an increasing global population and the increase in the numbers of people living
in urban centres, the trend of increasing urbanization and loss of natural ecosystems (and therefore
biodiversity) can be expected to continue. The density of people living in cities is very high compared
to more rural areas, so it could be argued that increasing urbanization overall provides an effective and
efficient way of housing a rapidly growing population, compared to less-dense housing solutions.
■ Deforestation and clearance of land for agriculture
Deforestation
Habitat loss due to deforestation is one of the major causes of biodiversity loss. This is especially
true when biodiverse ecosystems, such as tropical rainforests, are cleared.
Rainforests cover only 6% of the Earth’s surface, yet may be home to 50% of all species. The climate
in equatorial areas provides optimal conditions for photosynthesis and, therefore, the production of
food for consumer organisms.
Tropical rainforests are rich in natural resources such as timber and so are vulnerable to exploitation,
with an average of 1.5 hectares (equivalent to a football pitch) lost every 6 seconds in 2019.

Conversion of land for agriculture and mining

The increase in the world’s human population from around 3 billion (3 × 109) people in the 1950s
to over 7 billion people in 2023 (Figure A4.2.10) has led to increased demand for food. Conversion
of land to agriculture to produce food (Figure A4.2.13) has led to further habitat loss. Nearly 40% of
the Earth’s land surface is used for agriculture (Figure A4.2.14), with an area approximately the size
of South America used for crop production, and even more land (3.2–3.6 × 109 hectares) being used
to raise livestock such as cattle.
A4.2.7—Need for several approaches to conservation of biodiversity
No single approach by itself is sufficient, and different species require different measures. Include in situ conservation of species in natural
habitats, management of nature reserves, rewilding and reclamation of degraded ecosystems, ex situ conservation in zoos and botanic gardens
and storage of germ plasm in seed or tissue banks.

Conservation, in ecological terms, means striving to ‘keep what we have’. Conservation biology is the scientific study of Earth’s biodiversity with the
aim of protecting habitats and ecosystems, and therefore species, from human-made disturbances, such as deforestation and pollution.
Conservation activities aim to slow the rate of extinction caused by the knock-on effects of unsustainable exploitation of natural resources and to
maintain biotic interactions between species.
■ In situ conservation
In situ conservation is the conservation of species in their natural habitat. This means that endangered species, for example, are conserved in their
native habitat. Not only are the endangered animals protected, but also the habitat and ecosystem in which they live, leading to the preservation
of many other species. In situ conservation works within the boundaries of conservation areas or nature reserves.
In situ conservation may require active management of nature reserves or national parks. This may mean active clearing of overgrowth, limiting
predators, controlling poaching, controlling access, reintroducing species that have become locally extinct and removing alien species. In addition to
such measures, successfully protected areas also:
l provide vital habitat for indigenous species; this can include habitat and food for migrating species such as birds
l create community support for the area
l receive adequate funding and resources
l carry out relevant ecological research and monitoring
l play an important role in education
l are protected by legislation
l have policing and guarding policies
l give the site economic value.

The effect of biogeographic factors

Biogeographic factors affect species diversity and so need to be considered when planning nature reserves.
Island biogeography theory predicts that smaller islands of habitat will contain fewer species than larger islands. Therefore, it is inevitable that
protected areas will have lost some of the diversity seen in the original undisturbed ecosystem. The principles of island biogeography can be applied to
the design of reserves
Nature reserves that are better for conservation have the following features.
l They are large, so that:
l they support a greater range of habitats and, therefore, greater species
diversity
l there are higher population numbers of each species
l there is greater productivity at each trophic level, leading to longer food
chains and greater stability
l they can maintain top carnivores and large mammals.
l They have a low perimeter to area ratio to reduce edge effects. Fewer edge
effects mean more of the area is undisturbed. Edge conditions are very
different to those of the interior habitat (hotter, less humid and windier),
and so flora and fauna that are interior specialists cannot survive in edge
conditions. The best shape for a reserve is a circle as this has the lowest
edge to area ratio – it is better than an extended strip of land, or one that
has an undulating edge, even if the total area is the same.
l If areas are divided, then fragmented areas need to be in close proximity to
allow animals and plants to move between fragments, or there needs to be
corridors to join fragments.
l Gene flow between fragmented reserves is maintained by enabling
movement along corridors.
l Movement of large mammals and top carnivores between fragments is
maintained by corridors.
Rewilding and reclamation of degraded ecosystems

Other cases of in situ conservation involve ‘rewilding’ and reclamation of degraded ecosystems.
Rewilding aims to restore ecosystems and reverse declines in biodiversity by allowing wildlife and natural processes to reclaim areas no longer under
human management. It is a form of environmental conservation that can significantly increase biodiversity in an area. Rewilding reintroduces lost animal
species to natural environments, such as top predators that have a significant effect on the food web and trophic levels in an ecosystem. For example,
the US National Park Service began to reintroduce the grey wolf (Canis lupus) into Yellowstone National Park in the mid-1990s. This lowered the local
elk population (Cervus canadensis) population and their overgrazing of plants.
Rewilding has three main principles:

1 Core habitat areas that support biodiversity are established.

2 Connectivity: corridors of habitat connect the core areas, allowing movement of biodiversity between different parts of the landscape.
3 Carnivores: top predators are needed to maintain the ecological balance of communities.

Carnivores represent the apex predators within ecosystems whose presence and reintroduction within a landscape enables ecosystem restoration.

The benefits of rewilding include:

l Increasing storage of carbon from the atmosphere: for example, in the UK it is estimated that by restoring and protecting native woodland, peat bogs,
heaths and grasslands (a total area of over 6 million hectares), 47 million tonnes of CO2 per year could be captured and stored. This figure
is more than a tenth of current UK greenhouse gas emissions.
l Helping wildlife adapt to climate change: connections between different wildlife reserves allow animals to move and habitats to adapt as climate
change leads to the northward shift of ecosystems (as the temperature in northern latitudes, on average, warms). This has the potential to save a
significant number of species from climate-driven decline or extinction.
l Reversing biodiversity loss: rewilding allows a reversal of biodiversity decline and extinction.
l Supporting economic opportunities for local people: rewilding has the potential to help communities grow and thrive through nature-based enterprises,
production and employment opportunities.
l Improving health and well-being: reclaimed and restored areas provide clean water, healthy soils, flood defences, food and unpolluted air, all of which
support human health and well-being.
It’s important that everyone has access to natural environments, especially people who live in urban areas.

Ecosystem restoration means preventing, halting and reversing the damage caused to degraded ecosystems. Efforts to restore ecosystems and
species can involve active management of the land, for example replanting native trees to restore forest cover. Rewilding may involve
reorganizing and regenerating wildness in an ecologically degraded landscape. This may modify the biodiversity that would have originally been
present, perhaps to manage the landscape in the long term with maximum sustainability in a changing world (e.g. through climate change). Restoration
ecology aims to return an ecosystem to as close to its former state as possible after a major disturbance.
■ Ex situ conservation
Ex situ conservation is the preservation of species outside their natural habitats. For animals, this usually takes place in zoos, which carry out captive
breeding and reintroduction programmes:
l a small population is obtained from the wild or from other zoos l enclosures for animals are made as similar to their natural habitat as possible
l breeding can be assisted through artificial insemination.
Botanical gardens have a role in the ex situ conservation of plants, where both living collections and seed banks are used to store genetic diversity. The
storage of germ plasm represents a live information source for all the genes in a species of plant, which can be conserved for long periods and
regenerated whenever it is required in the future. Germ plasm conservation is the most successful method to conserve the genetic characteristics of
endangered and commercially valuable species.
Tissue banks store body tissue and can be used to provide material from which researchers can extract genomic DNA, potentially to restore endangered
or even extinct organisms.
Case study: The golden lion tamarin
The golden lion tamarin (Leontopithecus rosalia)
was critically endangered, but its conservation status has
improved due to human intervention. Found in the tropical
rainforests of Brazil, 90% of the golden lion tamarin’s original
habitat has been cut down and the remaining forest is small and
fragmented. The species is only found in one small area of Brazil
and so is especially vunerable to extinction. The monkey was
thought by some to carry human diseases, such as yellow fever
and malaria, and so was hunted to near extinction. The loss of
the species would have affected other species such as insects
and small lizards, which the monkey ate, causing those species
to become more numerous. Larger animals that preyed on the
monkey would decrease in number. Overall, the food chains
of the rainforest would become shorter, producing changes in
other trophic levels and imbalances in the forest food web.

Captive breeding programmes (ex situ conservation) in places such as Bristol Zoo in the UK have increased numbers, allowing release into the wild. There are also
efforts to preserve the native forests of the monkey in Brazil (in situ conservation), for example at the Reserva Biológica de Poço das Antas, near Rio de Janeiro. Now,
the numbers in the wild have increased from a low of 400 in the 1970s to about 1000 today.
The case of the golden lion tamarin indicates how both in situ and ex situ conservation is needed to conserve species effectively: combining both in situ (e.g. protected
areas) and ex situ (e.g. zoos and captive breeding) methods can be the best solution for species conservation in many instances.
A4.2.8—Selection of evolutionarily distinct and globally endangered species for conservation prioritization in the EDGE of Existence programme
Students should understand the rationale behind focusing conservation efforts on evolutionarily distinct and globally endangered species (EDGE).
NOS: Issues such as which species should be prioritized for conservation efforts have complex ethical, environmental, political, social, cultural
and economic implications and therefore need to be debated

■ International conventions on biodiversity

International conventions have shaped attitudes towards sustainability. The UN Conference on the Human Environment (Stockholm, 1972) was the first
time that the international community met to consider global environment and development needs together. It led to the Stockholm Declaration, which
played an essential role in setting targets and triggering action at both local and international levels.

In 1992, the UN Rio Earth Summit resulted in the Rio Declaration and Agenda 21:
l The Earth Summit was attended by 172 governments and set the agenda for the sustainable development of the Earth’s resources.
l The Earth Summit led to agreement on two legally binding conventions: the UN Convention on Biological Diversity (CBD) and the UN Framework
Convention on Climate Change (UNFCCC).
l Both the UNCBD and UNFCCC are governed by the Conference of the Parties (CoP), which meets either annually or biennially to assess the success
and future directions of the Convention. For example, CoP 15 of the CBD was held between 25 April and 8 May 2022, in Kunming, China.
The CBD developed the ‘Vision of the Strategic Plan for Biodiversity’ that ran between 2010 and 2020. Its stated aim was: ‘By 2050, biodiversity is
valued, conserved, restored and wisely used, maintaining ecosystem services, sustaining a healthy planet and delivering benefits essential for
all people.’
A ‘post-2020 Framework’ has now been put in place which seeks to ‘bring about a transformation in society’s relationship with biodiversity’. Both plans
highlight the need for ‘transformative change’ to better appreciate the value of biodiversity and to avert its loss.

■ Phylogenetic diversity and conservation

Phylogenetic diversity is an important aspect of biodiversity, as it measures the evolutionary history represented by a set of species. The extinction of a
species that represents an entire branch of the ‘tree of life’ means a significant loss of diversity, as well as the loss of an evolutionarily distinct species.
A practical methodology for applying the concept of phylogenetic diversity to conservation is being used in the ‘EDGE lists’ produced by the Zoological
Society of London (ZSL). EDGE (Evolutionarily Distinct and Globally Endangered) species are those which disproportionately represent threatened
phylogenetic diversity.
EDGE species are those that have an above-median Evolutionary Distinct (ED) score and are also threatened with extinction (Critically Endangered,
Endangered or Vulnerable on the IUCN Red List).
There are currently over 550 EDGE mammal species (around 10% of all species) and over 900 EDGE amphibian species (around 13% of all species).
Potential EDGE species are those with high ED scores but whose conservation status is unclear.
EDGE species identified so far include mammals, amphibians, birds, corals, reptiles, gymnosperms (a group of plants which include conifers) and
elasmobranchs (sharks, rays and skates).
EDGE species represent an opportunity to stop the loss of phylogenetic diversity. In 2012, the IUCN adopted a resolution that recognized the importance
of conserving threatened evolutionarily distinct lineages.