There are various kinds of landforms on earth, each needing certain conditions to exist. These conditions can change by nature itself or by human interaction. Deforestation is a form of human intervention that's causing a decrease in the world's forests, and an increase in cultivated and desert areas. Global temperatures are increasing, caused by pollution. Weather changes allready affect large areas of the globe, causing heavier rains and floodings in certain areas, melting glaciers and droughts elsewhere.