Habitat change

The human modification of the Earth’s land surface has been taking place for thousands of years for food and to obtain other resources. However, the current rate, extent and intensity of change is far greater than has been experienced ever before. That is driving unprecedented changes in ecosystems and environmental processes.

 

The conversion of primary forest to semi-natural, agricultural habitat is among the most extreme change (for example, loss of tropical and semi-tropical rainforest to palm oil plantations). Such deforestation has the potential to cause problems on a global scale and a clear link has been demonstrated between forest loss and climate change.

 

In addition, habitat losses can result from:

  • Changes in farming practices, such as intensity of cultivation and changes in crop types
  • Expansion of transport networks
  • Urban development
  • Mining and quarrying
  • Recreational use

 

Biodiversity is often reduced dramatically by changes in land use. The area and condition of suitable habitat can be reduced, patches of habitat can be lost and remaining habitat can become fragmented. After a change in use conditions may no longer be suitable for a species to survive and individuals may be unable to move elsewhere.

 

Rivers

In many countries, including most developed countries, it is rare to find a river that has not been profoundly altered by human use.  Natural rivers are dynamic and changeable with many freshwater and wetland habitats and species along their course that rely on the habitat. 

 

People have made intense use of rivers. They have been altered to provide energy, from water mills to modern hydroelectric power.  They are often straightened or canalised to free up land for farming and to carry flood waters away as quickly as possible. Many are blocked or impounded to form storage reservoirs.

 

Water is used for farming, industrial use and for drinking and is taken from rivers directly or from underground sources, both of which reduce river flows. Food has always been harvested from rivers and they are also used for transport and recreation. 

 

Some of these uses are in conflict with each other and not all are sustainable. For example, rivers are straightened, widened and canalised to protect nearby land, but over time changes can alter the performance of the river upstream and downstream leading to flooding elsewhere. Together with land use changes in the catchment, such as ploughing up grassland and improving agricultural drainage, it can exacerbate both droughts and floods.

 

Reservoirs for water storage also have an impact. They can interfere with water quality and flows downstream, with the migrations of fish and may be vulnerable to silting.

 

Human engineering of rivers has reduced biodiversity. However, sustainable approaches to management can prevent flooding by restoring natural, diverse river corridors and can deliver biodiversity increases too.