Habitat destruction
H stands for 'habitat destruction'
Forests all over the world are being cut down and burned for many reasons.
Forests in the tropics are cleared to make room for farms. But tropical forest soil is very poor, and so farmers have to keep moving on and destroying more and more forests to grow their crops.
International companies also cut down forests for their timber, or to make room for other plantations, in which most native animals and plants cannot survive.
Each year, 1% of the world's tropical forest is destroyed. This doesn't seem like much but it all adds up, and is not good news for native plant and animal species.
Wetlands - lakes, ponds, marshes, swamps and rivers - are also very threatened habitats.
Most wetlands in Europe and North America have been drained over the last two hundred years. This has affected the normal migration and breeding patterns of many water birds, which now are restricted to only a few remaining wetland areas.
Although natural habitats are often completely destroyed, they can also be broken up into lots of isolated patches.
These patches may be separated by roads, fields or human habitation, and may become too small to support the species that depend on them. This process of habitat fragmentation is the main reason for the decline of many animals and plants.
