Option G.4 – Conservation of Biodiversity

Option G.4 – Conservation of Biodiversity

G.4.1 – Explain the use of biotic indices and indicator species in monitoring environmental change

One of the major threats to biodiversity is the destruction of rainforest. Human activity is causing changes to many biomes worldwide, such as through pollution, which may not always be self-evident. In order for conservation of natural environments to happen, there must be early detection of environmental change. As some organisms are particularly sensitive or vulnerable to environmental change, their numbers and conditions can function as biological indicators (or biotic indices) of environmental change and the health of an ecosystem. Lichens and mosses are indicator species of environmental change.


Lichens are dual organisms. Their body contains fungal and algal components living together for mutual benefit. There are many species in existence, and they often occur in hostile habitats. The compact fungal hyphae absorb water and retains water and ions, while the algal part carries out photosynthesis.

Lichens, along with mosses, are susceptible to air-borne pollutants dissolved in rainwater, as their surfaces are not protected by a waxy cuticle. Since the thallus will absorb various pollutants, they can be analysed for heavy metal ions. Their growth rate is affected by pollution, which can serve as a valuable indicator.

Fresh Water Pollution

Aquatic plant growth becomes abnormally high in water enriched with inorganic ions. This may be due to pollution from raw sewerage and stockyard effluent – manure or silage liquors. Excessive or incorrect use of fertilizers on farm crops results in it leaking from the soil by rain. Increase in concentration of ammonium, nitrate and phosphate ion increases plant growth as they are beneficial to plants.

Waters that are ion-enriched in summer with raised temperatures undergo a plant population explosion. This is often referred to as an algal bloom because algae are involved and, as many are unicellular, their growth rates are spectacular. When plant life is in excess in polluted, it is an example of eutrophication.

In marine habitats, the extensive seasonal algal blooms of the oceans can be observed in satellite images.

After the algal bloom has died back, saprotrophic, aerobic bacteria will decay the organic remains of the plants. The water becomes deoxygenated, causing anaerobic decay and hydrogen sulfide formation. While some organisms can survive these conditions, many aquatic organisms like fish will die due to absence of dissolved oxygen, as well as the presence of hydrogen sulfide. Changing populations of invertebrate aquatic animals are indicators of the degree of pollution and recovery. Such species may be classes according to how well they tolerate pollution and given a corresponding value. This allows a quantitative value to be given to the state of the waterway.

The effect of pollution of a river can be observed by eye and measured by chemical analysis. This may include testing dissolved oxygen concentration, the conductivity and concentration of organic matter.

Red Data Books

The rate of extinctions is very high. Environmentalists will seek the survival of endangered species by initiating and maintaining local, national and international action. The updating of Red Data Books is co-ordinated by the International Union for the Conservation of Nature and Nature Reserves. The Red Data Books list endangered species, and identify those which need special conservation efforts. Health and general well-being of populations of these organisms are indicators of environmental change. Practical conservation steps may include the designation and maintenance of

Practical conservation steps may include the designation and maintenance of nature reserves, botanical and zoological gardens (with captive breeding programmes) and the establishment of viable seed banks. These will combat the loss of endangered species and the habitats which support them.

G.4.2 – Outline the factors that contributed to the extinction of one named species

New species evolve, while other species that are less suited to their environment will become extinct

Tasmanian tiger

Tasmanian Tiger (Thylacinus cynocephalus) became extinct after the arrival of European settlers in Tasmania, Australia, in tragic period of conflict due to the introduction of sheep. European settlers were puzzled by it and feared, and would kill it when they could Tasmanian tigers were shy creatures and avoided contact with humans. They would usually give up without a struggle when captured, many dying suddenly of apparent shock.


They were widespread throughout Tasmania, and would feed on the introduced sheep. As a result, the parliament placed a price on the head of the tiger, which caused numbers to rapidly decline. The population dwindled to the point that there were only a few remaining in zoos.

However, the Tasmanian Tiger did not breed well in zoos. They lived in captivity for about 9 years. The last captive tiger died in Hobart in 1936 and Tasmanian Tigers were declared extinct by international standards in 1986.



Aboriginal rock paintings and fossils suggest that they once lived on mainland Australia and New Guinea, and are believed to have become extinct there due to predation and competition with dingos.




The dodo was a forest-dwelling bird that is related to modern species of pigeons. They were large birds that grew to about a metre long and weighed approximately 20kg. They nested on the ground, where they would rear their young. Dodos fed on fruit and seeds that fell to the ground from forest trees.


The dodo was extinct by 1681, which came about as a result of the spice trade. The European explorers secretly used Mauritius to grow spice plants, stop over port for restocking and farming, people migrated there and smuggling seeds and plants.

G.4.3 – Outline the biogeographical features of nature reserves that promote the conservation of diversity

Biological conservation can be attempted by setting aside land for restricted access and controlled use to allow the local maintenance of biodiversity. Nature reserves, game parks and National Parks serve as a solution to extinction pressures on wildlife. They represent habitats of different descriptions, some of their conservation work being carried out by volunteers all over the world.

A nature reserve will control any alien species, removing any that are not originally supposed to be there. Areas degraded by human impact are restored through reforestation and species reintroduction. Threatened species are helped to recover, and human exploitation is controlled.


The area enclosed in a nature reserve is important. There is usually an optimum size for reserves, with an area too small being ineffective, and one too large securing no greater diversity. This will vary according to species, size and lifestyle of the threatened species it is trying to protect. Larger nature reserves tend to promote better conservation of diversity than small ones.

Edge Effect

There is also an edge effect for a given reserve. A compact reserve with minimal perimeter is more effective than one with an extensive interface between its perimeter and surroundings. The uses of the surroundings of the reserve are also important, as it may indirectly support the reserve’s wildlife. The ecology of the edges of a reserve is different from the central areas as a result of these edge effects.


Geographical isolation is another important feature. Reserves in close proximity of each other are more effective than those at great proximity. Corridors of land may also overcome the disadvantage of small reserves in need of a larger provision as they increase the total size of the reserve. For example, in agricultural areas, hedgerows may be protected from contact with the pesticide treatments that nearby crops receive. Another example is tunnels under busy roads, allowing for movement of organisms between different parts of a fragmented habitat. This way, organisms can move around for feeding and breeding, maintaining genetic diversity.

G.4.4 – Discuss the role of active management techniques in conservation

Conservation is an active process, involving using knowledge of ecology of habitats (both biota and abiotic factors), in order to manage the environment of the nature reserve, and maintain biodiversity.

Active management helps to maintain an endangered species or habitat. Wildlife can be secured under favourable conditions for contemplation, education or research. These methods counterbalance unchecked exploitive management in natural resources, such as deforestation and agriculture. Degraded areas must be restored and succession beyong the desired level must be prevented

Proper conservation relies on a number of factors:


G.4.5 – Discuss the advantages of in situ conservation of endangered species (terrestrial and aquatic nature reserves)

Endangered species tend to have very low population numbers, and are in danger of becoming extinct. They are conserved for our own benefit, including a larger gene pool for genetic engineers, as well as sources of compounds with medical value. Some wild organisms are also more efficient energy converters that existing crops and herbs in particular ecosystems. Diversity of both flora and fauna is also essential for the continuation of the process of evolution of new
species in response to the changing environments of the Earth.

These reserves can often have commercial use, as they provide tourist venues.



G.4.6 – Outline the use ex situ conservation measures, including captive breeding of animals, botanic gardens and seed banks

Ex situ measures may take place complementary to in situ conservation, as they have a valuable role to play in the recovery of endangered species.

Captive Breeding

When a habitat is destroyed, the species will need to be moved to another location to preserve it. Captive breeding programmes now make good use of the resources available at zoos, maintaining the genetic stock of rare and endangered species. Through cooperation between zoos, and sometimes artificial insemination, the genetic problems arising from limited numbers to act as parents are overcome. The animals in zoos are also available to participate in breeding programmes for longer as they have a longer life expectancy.

Artificial propagation of plants may also take place, with them subsequently being returned to the wild.

These programmes are usually highly successful. However, the young do not grow up in the wild, so they do not have as much opportunity to learn from their parents and peers.

Healthy individuals are produced in good numbers, and advantage against natural predators during re-introduction. Zoos have sites for the public to visit, which contributes to public education and awareness on the environmental crisis.

Botanic Gardens

These can also be used when a habitat has been destroyed. Botanic gardens have sites for the public to visit, which contributes to public education and awareness on the environmental crisis. In a similar way, zoos and aquaria will promote public awareness and facilitate research whilst conserving the species.

Gene Banks

Seed banks are a convenient and efficient way of maintaining the genetic material of endangered plants, with similarities to the ways seeds may survive long periods in nature.

Similar methods are sperm and ova banks and field banks. With these collections, the seeds can be used if the species becomes endangered. These seeds are carefully stored so that they may remain viable for up to 100 years.