Always start with the soil.
So what's wrong with pesticides and fertilizers? They seem, on the surface, to be good things. One kills pests while the other helps things grow. Remember, always start with the soil. A healthy soil already has everything it needs to help things grow. Now let's be clear, not all fertilizers and pesticides are created equally. There are organic methods of fertilizing and getting rid of pests. There are chemical methods. These fertilizers do not feed the soil, they feed the plant. But their residue stays in the soil and then gets into the water system, into streams, rivers and ultimately the ocean. In the ocean, the extra nutrients in the fertilizers promote algae blooms that then decompose and deplete oxygen needed by fish and other aquatic life. This process can potentially create "dead zones".
Pesticides are not always discriminating in what they kill. Beneficial insects and organisms can be collateral damage. Studies show that regular use of herbicides, fungicides, and insecticides decreases the number and diversity of beneficial soil life, from earthworms down to bacteria and fungi. And consider the other wildlife and the effect on the food chain. Also, increased pesticide and soluble fertilizer use correlates with increasing soil compaction and acidification. So remember, whether gardening, farming or landscaping, always start with the soil.