How can farming negatively affect soil?

Answer 1

There are a number of impacts of farming.

Some may be positive, or mildly positive. Tilling may aerate the soil. Organic fertilizers such as manure may add to and improve the soil. Tilling crop waste into the soil may also help it. Removing rocks may also "improve" at least the agricultural aspects of the soil.

But, there are also negative aspects. Native plants and vegetation are often lost. Characteristics of the land not favorable to farming may be changed, such as draining swampland, and thus destroying the native swamp habitat. Rock removal or adding fill do essentially permanent changes to the soil, good or bad.

Much of the Southwest's soil has a few layers including the Cryptobiotic crust, and the Caliche layer that help stabilize the soil, but are very slow to regenerate and are severely damaged by farming and other human activities.

In other places, "turf" and whatever was binding the soil together is broken leading to soil instability.

Poor farming practices can open the pathways for erosion and soil loss.

There can be soil depletion. I.E. When the plants are harvested, the soil nutrients are lost.

Farming practices can disrupt the local ecosystem. This can be especially true if forests are cut to make way for farming. Especially in the equatorial rain forests where there is extremely fertile land, but also an extremely complex ecosystem. And sometimes this can also cause regional drying of the soil or warming of temperatures.

Most farming practices use large "single" crops that are susceptible to disease. They also often use pesticides and poisons to control pests and diseases... many (or their derivatives) which can get into the soil, or in the worst case, penetrate into deep layers of the soil and even down to the groundwater. This can also be true with highly concentrated livestock such as in feedlots, large hog farms, or large chicken farms.

Finally, too high of animal density (out grazing) just leaves mud or dust behind.

There are many "invasive species" caused by planting crops or plants that got out of control.

Sludge from human waste can be great fertilizer, but also carries heavy metals and derivatives of whatever was in the waste stream, and contaminate the farmland.

Not really a soil issue, but where do all the animals (and native plants) go that were living somewhere BEFORE the farmland?

Irrigation can lower groundwater levels and cause sinkholes.

Irrigation has also caused salt layers to raise up in parts of Nevada and Utah, and poisoning the land.

There are increasing fights over water distribution for both crops and human use. And, movement of water from one place to another can leave previously "green" places without water.

Irrigation also often includes dams which cover soil with water. It also changes river flow, sediment flow and sediment settling patterns, fish migration, etc.

With dams, one also has flood control. One aspect of floods is the redistribution and deposition of soil. For example the Mississippi valley regularly flooded and deposited fresh new fertile soil in the valley. This has been blocked by dikes and dams. The soil settles behind dams and must be dredged, or flows all the way out into the Gulf of Mexico. New Orleans is sinking because soil that used to be deposited in New Orleans is no longer being deposited there. But, in a sense, the same thing is happening to all of the farms from the Great Lakes down to the Gulf of Mexico, including along the Missouri and Ohio rivers and other tributaries.

Fences and roads now break up the entire country and limit the free range of native animals. And, since many native animals are considered "pests", they are killed or excluded from farmland.

We've changed the face of the planet. There are fields where there once were trees. There are roads where there was wilderness. Thousands of square miles of asphalt. Irrigation where there was dryland. Huge herds of animals have been decimated, and if they are lucky, put on small reserves.

I suppose my question that I've often proposed is how much of the surface of the planet should be dedicated to serving a single species? And, should that species be allowed to take the choicest of land for their exclusive use?