- Diversity is vital
- Beauty in jeopardy
- Ecological services
- What destroys biodiversity?
- The human manipulator
- Dialogue for Sustainability
- Changing Course
What destroys Biodiversity?
Habitat loss, overexploitation and pollution are the three most serious threats to biodiversity. Human actions that contribute significantly to these threats are infrastructure development (roads and housing), clearing land for crops, overfishing, and emissions of polluting substances from industry and agriculture.
In terrestrial and inland water ecosystems, human activities often lead to the loss and fragmentation of habitats. The ensuing smaller patches are more vulnerable to outside influence and tend to support smaller populations of species. Consequently, these populations and ecosystems are at higher risk of local extinction.
Farming has reshaped the planet more than any other human activity. Today, nearly a quarter of the Earth’s surface is now cultivated. The underlying cause, increased demand for food, is brought about by the escalating global human population, and by increases in our consumption of meat. As a result, we see the continued destruction or degradation of areas important for bio-diversity. For example, around 13 million hectares of forest – equivalent to the area of Greece or Nicaragua – are being lost each year.
We also see the loss of habitat in other ecosystems. The extent of live coral cover in the Caribbean is estimated to have declined by 80% in the last three decades, and some 35% of mangroves have been lost in the past twenty years in countries for which adequate data is available.
The demand for higher crop yields has led to intensified use of fertilizers. These leak into our natural ecosystems where excessive levels of the plant nutrients nitrogen and phosphorus are now a cause for major concern. The increase of reactive nitrogen in ecosystems changes ecological balances and brings about drastic changes in plant communities, generally favouring common species at the expense of more specialised and rare species of, for example, plants and insects. Soluble nitrogen from fertilizers also leaks from soils into the groundwater, rivers and lakes. Here the excess nutrients (eutrophication) stimulate excessive plant growth, or algal blooms, and the creation of anoxic (oxygen-free) zones where no life can exist.
Overfishing is also another problem caused by our food demand: three-quarters of all edible fish stocks are completely exhausted or overexploited. And yet, many fishing practises result in the discarding of up to 80–90% of the catches – because the fish are too small or not the species the fishing boat aims to catch. Ironically, size matters a lot in the fish reproduction cycle. Thus, as a rule of thumb, when a female fish grows four times bigger her egg production increases 64 times and is of better quality.
The first steps in a positive direction are underway: more farmers are managing their land with a minimal impact upon nature, and consumers are expressing ever greater demand for products grown using organic management techniques.
The most important tool to stop the process of habitat loss is to establish net-works of protected areas. This appears achievable soon, and it is one of the goals of the Convention on Biological Diversity to give protected status to 10% of all terrestrial ecosystem types. However, biodiversity should also be maintained outside of reserves, through supporting sustainable management practices and by using quotas and licences to counter overexploitation and pollution.
Next chapter: The human manipulator
World Footprint: The ecological footprint of humankind
In 2003 every human being on this earth was able to consume 1,8 global hectar without destroying nature.
The ecological footprint measures the annual consumption of natural resources by human beings. Using published statistics, it calculates the area of land needed to sustain a defined human population at a set material standard, based on the population’s use of energy, food, building material and other consumables. Although the concept does not provide a comprehensive assessment of demands on nature, it is a useful accounting tool that demonstrates the effect of human consumption on the productive capacity of the Earth.
Currently, the average ecological footprint is 2.2 global hectar per person – with considerable regional disparities in consumption. Citizens of North-America, Europe and Australia generally emit more pollutants, and consume more per person than the citizens of Asia, Africa and Latin America. Humankind as a whole currently consumes 25 percent than it can produce with sustainable cropping. This is the case, for example, when people clear forests but do not replant them, when plantations are created whose artificial irrigation causes rivers and lakes to dry up or when carbon dioxide is emitted faster than it can be absorbed by forests, soils or oceans.
We need to reduce our ecological footprint by 2010, to reduce biodiversity loss associated with the overuse of natural resources and ecological services.