In the article, Pimentel et al say:
Soil erosion is a major environmental threat to the sustainability and productive capacity of agriculture. During the last 40 years, nearly one-third of the worlds arable land has been lost by erosion and continues to be lost at a rate of more than 10 million hectares per year. With the addition of a quarter of a million people each day, the world population's food demand is increasing at a time when per capita food productivity is beginning to decline.
The article states:
"In the United States, an estimated 4 X 10^9 tons of soil and 130 x 10^9 tons of water are lost from the 160 x 10^6 ha of cropland each year. This translates into an on-site economic loss of more than $27 billion each year, of which $20 billion is for replacement of nutrients (50) and $7 billion for lost water and soil depth (Table 2). The most significant component of this cost is the loss of soil nutrients."
Pimentel et al state that the total on and off-site costs of damages by wind and water erosion and the cost of erosion prevention each year is 44,399,000,000.
These very large estimates of the costs of erosion are bound to trigger much debate during the Farm Bill process as Congress considers the costs and the benefits of continuing the Conservation Reserve Program and compliance policy.