Due to their different requirements, species distribution and abundance is affected by variation in temperature and moisture. This can clearly be seen on mountain slopes; we can distinguish vegetation belts or layers, marked by the dominant species of trees or shrubs. For example, on many volcanoes in Mexico, there is the oak belt of 2400 to 2800 m, the pine forests of 2800 to 4000, the bunch grasses of 4000 to 4500 and above this, the snow line.

Climatic changes affect species distribution and move these belts upwards with warming and downwards in periods of cooling. Changes in humidity also have similar impacts. Therefore, with the rapid global warming we are experiencing, species can leave their protected areas. It is important to make predictions about changes in the distribution of flora and fauna in order to conserve them.