There are a lot of risks to using pesticides. Unfortunately in my job, I see the risk, the consequences all the time of using pesticides, the main one being dead waterways, no fish, no bugs, overgrown with algae. I would agree that in a few cases pesticides may be necessary, but generally less toxic pesticides, better managed application of those pesticides, and using those pesticides after monitoring the crop pest load, would solve a lot of our problems.
The thing I see most people assume though and I see it in this question, is that pesticides are only a problem in agriculture. That is NOT in fact the case. As a pesticide regulator, we are seeing at least half the problem of pesticides in urban areas, where people overspray their lawn because they think they have too, people emptying out an entire can of raid on an ant's nest, and then the pesticide either poisons their kids, pets or runs into the waterways.
Back to your question, there are TONS of alternatives, including realizing that a few pests are okay, not overwatering, spacing plants out....
A cool website that I use a lot that has a lot of info (that you can cite if this is homework) is
http://ipm.ucdavis.edu . I recommend it because it can give you the easy understanding or more information if you want it. It is peer-reviewed I think, and just a really good reliable source about how to manage pests rather than spray for them.