The pie chart below shows the main reasons why agricultural land becomes less productive. The table shows how these causes affected three regions of the world during the 1990's.

The pie chart illustrates what main factors caused agricultural land to be less productive. The table provides information about shares of these reasons on three different parts of the world and overall degradation of these regions during the 1990's.

It is clear from the pie chart that,over-grazing is the biggest cause of the problem(35%), followed by deforestation and over-cultivation(30% and 28% respectively). The remaining 7% of the reasons, which made lands useless, is represented by other factors.

Turning to the table, it is obvious that, during 1990's, in Europe deforestation caused 9.8% of agricultural land to become out of use. Over-cultivation came second here at 7.7% with over-grazing representing only 5.5% of the total land degredation. In contrast, in Oceania 11.3% of the total was made up by over-grazing and deforestation came second at 1.7%.

Interestingly, here over-cultivation was not an issue at all. When it comes to North America, generally, lands here are the least degraded(5% totally) compared to other two regions. Over-cultivation was the main reason of degredation here during 1990's (3.3%). About 2 times less land was degraded because of over-grazing with deforestration being almost insignificant at 0.2%.