Herbicides are widely used in commercial agriculture and home gardening. They are used to control competitive weeds and plants that compete with crops for nutrients and water. They are used by home gardeners to reduce the amount of labor required for vigilant hand weeding of lawns and flower beds and sidewalk cracks. Herbicides have ancillary and unintended consequences that are often worse than the original problem they were invoked to solve. Herbicides can build up in soil, making replanting troublesome; they can runoff and leach into the groundwater; they can build resistance in the plants they were meant to kill; and they can remain in the tissues of plants and be consumed by animals and humans who eat them.
Leaching Into the Soil & Water Table
Herbicides are sprayed onto the soil surface or directly onto weeds to disrupt the growth cycle, prevent propagation and kill the weed. When areas are irrigated or rains come the herbicide is washed deep into or across the soil and can travel wider than you might imagine. Nearby streams, ponds and lakes can be affected, groundwater can become tainted and water that is put into a community's wastewater systems will either be recycled or dumped into yet larger bodies of water.
Triggering Herbicide Resistance
As with the strains of disease that become resistant to antibiotics, plants and weeds constantly exposed to herbicides can develop a resistance to their powers. This triggers a need for ever-increasing doses or more potent formulations that can be even more damaging to the surrounding plants, soil and water. Resistance is a common biological adaptation and is a significant problem with ubiquitous use of herbicides.
Run-Off & Ancillary Plant Death
Herbicides intended for weeds on a lawn that are growing next to a flower bed or fruit tree cannot always distinguish between the two and ancillary plant kill is a major problem with herbicides. Whether by accidental overspray or wind shift, herbicide-laden water runoff or soil leaching into nearby plants not immune to the formulation can suffer damage, weakening of performance or death.