Human effects on ecosystems

In a nutshell

Humans are able to manipulate the environment in ways that have profound impacts on various ecosystems. This summary discusses the effects that humans have on the ecosystem, the impact that treaties have had on global biodiversity and the importance of science communication.

Human influences on ecosystems

Medical advances, technological advances and improved living conditions have decreased the death rate and increased the birth rate of humans. As a result, population size has increased dramatically over the last $200\ years$ . Human pressure on resources and the environment have therefore increased.

Example

A prime example of the impact of humans on the ecosystem is the Atlantic cod (Gadus morhua) population. This population was thriving until large scale commercial fishing caused the cod population to collapse in $1992$ . Canadian authorities banned the fishing of the Atlantic cod, which led to many people losing their livelihoods. Despite this action, the cod population has still not recovered. Since then, organisations such as the Marine Stewardship Council have been established to enforce codes of practice among fisheries.

Impact of treaties on global biodiversity

Many animals, such as tigers and elephants, are at a high risk of poaching. The Convention on International Trade in Endangered Species of wild fauna and flora (CITES) was established to protect endangered species by controlling their movement and the use of their products.

Under CITES, the import and export of these products requires licenses and agreements by multiple parties. This prevents the removal of species from their natural habitats for commercial reasons and helps to protect the natural ecosystems.

Climate change

Another impact that humans have on the ecosystem is climate change. Carbon dioxide and other gases exist naturally in the atmosphere, however levels are increasing rapidly due to human activity.

Greenhouse effect

The greenhouse effect is described below.

Biology; Ecosystems; KS5 Year 12; Human effects on ecosystems

1.	Infrared radiation provided by the sun.
2.	Human activities produce greenhouse gases such as carbon dioxide and methane. These gases build up in the upper atmosphere.
3.	The gases then absorb infrared radiation that is reflected from the Earth's surface. The increased concentration of these gases in the atmosphere increases the greenhouse effect and causes the mean temperature of the Earth's surface to increase.

Evidence for climate change

Evidence	Explanation
Melting polar ice caps	Increased global air temperatures have caused the ice caps in regions such as the Arctic to melt. Since $1979$ , the size of the ice caps in the summer has decreased by an average of $20\%$ . If this decline continues, there will be likely no ice in the summer by $2060$ .
Rising sea levels	Sea levels rise for various reasons, including thermal expansion of the water due to global warming and also due to the melting of ice. There is an acceleration in the rate of increase of the sea levels which threatens to flood and destroy low-lying islands such as Bangladesh.
Coral bleaching	Algae and coral have a symbiotic relationship which gives coral its distinctive colouring. However, when then there is an environmental stressor, like increased water temperatures, the relationship breaks down and the coral begins to die.

Science communication

Scientific evidence is validated through communication and evidence. The table below details different aspects of science communication and how these validate scientific work.

Communication method	Description
Scientific journals	Scientists will publish details of their experiments and investigations in scientific journals. These will provide an introduction into the topic of research, the full methodology, data, analysis and conclusions. Scientific journals are available across the globe so scientists from all over the world will be able to read and build on papers they have read. Example Nature is a well-known scientific journal.
Peer review	Peer review is carried out on papers before they are published. The paper is scrutinised by expert scientists to ensure the data they present is correct and their conclusions are valid.
Conferences	Conferences are often organised by universities or research institutions. These give scientists an opportunity to present and discuss their published work.