Agriculture is the practice of raising crops and livestock for human use and consumption. It always  and it’s impacts on global environment have increased when Green Revolution began, around 1945. It’s environmental effects include:

  • Alterations of the Earth’s hydrologic cycle;
  • Increased levels of atmospheric greenhouse gases;
  • Decreased biodiversity;
  • Accelerated rates of soil erosion;
  • Rapid spread of eutrophication in freshwater and marine ecosystems.

You can read more about these consequences here.

The human population has grown and so have the amount of land and resources given to agriculture, which currently covers 38% of Earth’s land surface. Most of our food and fiber are obtained from cropland, land used to raise plants for human use; and rangeland or pasture, which is land used for grazing livestock. The large-scale mechanization and fossil fuel combustion enabled farmers to replace horses and oxen with faster and more powerful means of working with crops and livestock. This was the agricultural revolution, and it allowed the increase of food production by intensifying irrigation; introduction of synthetic fertilizers; and the use of chemical pesticides reduced competition from weeds and herbivory by crop pests.

Modern industrialized agriculture enabled us to feed more people at a very high ecological price. Industrial agriculture can remove forests; destroy wetlands; turn grasslands to deserts; diminish biodiversity; encourage invasive species; pollute soil; air and water with toxic chemicals; and allow fertile soil to be blown and washed away.

Even though we  have more food to feed more people, political obstacles and inefficiencies in distribution makes 850 milion people in developing countries without enough to eat. In adition, although human population growth has sloewd, we can still expect our numbers to swell to 9 bilion by the middle of this century. Therefore, the kind of word we’ll live in then will depend on choices make now, and knowing  how to make food supply sustainable , maintaining healthy soil, water and biodiversity is one of them. Agricultural scientists and policymakers pursue a goal of food security, the guarantee of an adequate and reliable food supply available to all people at all times.

There are some farming techniques that can reduce the impacts of conventional cultivation on soils. Those are:

  • Crop rotation – the type of crop grown in a field is alternated from one season or year to the next. This method can return nutrients to the soil, break cycles of disease associated with continous cropping, minimize erosion that might come from letting fielts lie fallow, and reduce insect pests, because if an insect is adapted to feed and lay eggs on one crop, planting a different type of crop will leave its offspring with nothing to eat. The crop rotation works if one of the rotated crops are legumes, because they have specialized bacteria on their roots, responsible for fixing nitrogen, revitalizing soil that the previous crop had partially depleated of nutrients;

  • Contour farming - cultivation on slopes, even though water might erode the soil more easily. Farmers plow furrows sideways across a hillside, perpendicular to its slope and follow the natural contour of the land to help prevent formation of gullies;

  • Terracing – the most effective method for preventing erosion, terracing consists on making levels platforms to contain water from irrigation and precipitation. It transforms slopes into series of steps like a staircase, enabling farmers to cultivate hilly land without losing huge amounts of soil to water erosion;

  • Intercropping – also minimize erosion because it consist on planting different types of crops in alternating bands or other spatially mixed arrangements. Intercropping provides more ground cover and reduces vulnerability to insects and disease;

  • Shelterbelts or windbreaks- used to reduce erosion from wind. Consists on the plantation of rows of trees or other tall, perenial plant along the edges or fields to slow the wind;

  • No-till farming – a tractor pulls a “no-till drill” that cuts furrows through the topsoil and crop residue, drops seeds into the furrow, and closes it over the seeds. A dose of fertilizer might be added to the soil along with the seed.