2. Biodiversity

What you need to know...
  • What is biodiversity?
  • How is the human population growing?
  • How does the growth of the human population impact on biodiversity?
  • How do natural disasters impact on biodiversity?
Biodiversity is the variety of living things in an ecosystem.  Areas with high numbers of many different species are known as biodiversity hotspots. The Amazon Rainforest is one of our planet's top biodiversity hotspots. It is the world's largest area of tropical rainforest and 10% of the world's known species live there. 
You do not need to go all the way to South America to see biodiversity. Scotland has a huge range of animal and plant species present in its many varied habitats such as pine martens, red squirrels, hares, rabbits, red deer and wild cats. There are even two species found in Scotland which are found nowhere else on our planet - the Scottish crossbill and Scottish primrose.
Scottish Primrose picture from Wikimedia Commons

Growth of the Human Population

For most of human history, the human population has grown at a slow steady rate. However, in the last 200 years the world population has grown very quickly - from one billion to seven billion. The reason for this huge increase is that humans have been able to overcome many of the factors that were previously limiting our population. Agriculture has allowed us to grow increasing amount of food. Scientific advancements in medicine have reduced the spread of disease and increased our life expectancy. Sanitation has also provided more safe drinking water and resulted in hygienic disposal of waste that both again prevent disease and reduce death rates.

Impact of Human Population Growth on Biodiversity
An increasing human population is presenting a huge challenge to our planet. 
  • DeforestationDeforestation is when trees are removed from an area of forest at an unsustainable rate. Deforestation may be carried out to provide wood for fuel, or to provide timber for building materials. Sometimes deforestation is carried out to provide space to keep livestock or to create space for new buildings. Whatever the reason, deforestation is having a very negative impact on biodiversity as plant species are destroyed and habitats for important species are lost. 
  • Overfishing - Overfishing is when fish are being caught at a rate faster than the ecosystem can replace them. A scientific report estimated that the number of large ocean fish has been reduced to just 10% of the population that had existed before overfishing began. Overfishing reduces the biodiversity of those fish that are being caught, but also those which are caught by accident. Important food chains are also being disrupted affecting the biodiversity of whole ocean ecosystems.
  • Intensive agriculture - Intensive agriculture practices include using fertilisers and pesticides, growing high-yield crops, and keeping animals indoors. While this is successful in increasing the amount of food available for the human population, there are dire consequences for biodiversity. Herbicides and pesticides can sometimes kill animals and plants other than those pest species being targeted. Large areas of land can be cleared to grow one high-yield crop destroying important habitats and reducing soil quality. Fertilisers may need to added to keep the soil fertile but this can run off into rivers causing algal blooms. Keeping animals indoors is seen as being unethical by many people who feel that it is not natural for the animals to be kept like this.
  • Genetic pollution - Genetic pollution describes the mixing of genes from a genetically engineered organism to a wild population. For example, if a farmer is growing a genetically engineered crop in his fields, there is little to stop pollen from this crop being blown into neighbouring non-GM fields. The genetic information carried in the pollen could mix with plants in the non-GM fields with unpredictable results. Once this has happened it is impossible to reverse these results.
  • Global Warming - Global warming is the continuing rise in the average temperature of our Earth. While some changes in our climate are natural, the significant warming that has been taking place in recent years is a result of greenhouse gases that have been released into the atmosphere by humans. Learn more about the greenhouse effect using this great National Geographic link. The effect of global warming on biodiversity is very concerning. Melting glaciers and sea ice are leading to rising sea levels and loss of habitats. The change in temperature has already caused some animals to move further north to cooler areas. Those that are not able to move or adapt will die out and become extinct. Floods and droughts may also become more common.
  • Acid Rain - Is rain that is unusually acidic. This is due to the presence of pollution in the air which mixes with water in the air to form acid. When acid rain falls it can makes the soil acid too. Many plants cannot tolerate this increase in acidity and they fail to grow properly or can even die. Acid rain can also run into rivers and streams causing fish and aquatic plants to die.
  • Oil and chemical spills - Oil gets into the feathers of birds and the fur of mammals. This means they do not float as easily in the water and makes them more vulnerable to temperature changes. When the animals try and clean themselves they eat the oil which is toxic.
Natural Disasters
Natural disasters also have an impact on biodiversity. Examples of disasters which can occur naturally include: forest fires, earthquakes, volcanic activity, tsumanis and wind. 
Well established ecosystems can tolerate some natural disasters. It is found that many plant species can grow back after forest fires, or a tree felled by wind can open up an area for new species to flourish. However, the weaker our ecosystems are the less able they are to recover from such natural disasters and again biodiversity suffers.