Moreover, many people value species and ecosystems for aesthetic, moral, or spiritual reasons, even if they do not use them. Although all these benefits are real, many of them do not enter markets. This is one of the reasons biodiversity tends to be undervalued. Agriculture has played a major role in this process because crop and livestock production affect the largest portion of the earth's surface and are the world's biggest users of land and freshwater. In many countries the conversion of land to agriculture is closely related to logging because many logged areas are later cultivated, and roads built for logging facilitate new settlement.
Habitat conversion can lead directly to the extinction of species.
Even if species survive the conversion of part of their habitat, their long-term survival may be threatened by fragmentation and disturbance of the rest of the ecosystem. In Hawaii, for example, the natural ecosystem has been under continuous attack by introduced plant and animal species. Some birds unique to Hawaii build their nests on the ground and are now threatened by pigs and mongoose, both introduced species. Species are also threatened by agricultural chemicals and by changes in water sources caused by human use. Protected areas are on the rise Protection of endangered ecosystems is one way to ensure that biodiversity and its many benefits are preserved for current and future generations.