As shown in the pie chart, the most harmful cause worldwide is over grazing which covers 35 percent of total causes. As we can see, the second adverse phenomenon is deforestation (by 5 units less--> is this a phrase?) and the last one is over cultivation (why by?) 28 percent of the total (opposing?) effects.
According to the table, European agricultural productivity has been affected in the most significant way. As can be observed (you have overused phrases beginning with as), the total land degraded in Europe is 23 percent, while at the same time it is 13 percent in Oceania and 5 percent in North America.
However, from the table it may be inferred that there is no over cultivation in Oceania, albeit this phenomenon is the third cause of worldwide degradation.
as we could see in the pie chart, there is a 7 percent of other factors that have not been estimated yet, which contribute to the decreased agricultural productivity. (Why refer back to the pie chart when you have not sufficiently covered the data in the table?)