A、By using satellite images, maps, etc. B、By studying specific fanning methods. C、By studying the variation of human population.

Experts say some farming activities are seriously damaging Earth’s environment. Bad farming methods can damage soil, forests and water supplies. They also have caused some plants and animals to disappear.
    Two groups now say that bad farming methods are threatening the ability of farmers to produce enough food to feed the world population in the future.
    The groups used satellite images, maps and modern equipment to study the effect of agriculture oil the enrichment. The study found that the destruction of soil is widespread, important organic nutrients being removed from farmland.
    Agriculture uses seventy percent of the freshwater in the world each year. The study found that many farmers wasting water supplies. In addition, chemicals designed to protect crops may pollute waterways.
    The report aim says as much as thirty percent of the word’s forests have been cut down so the land could be used for agriculture. This has led to a seven loss of wildlife and their environments.