what do pesticides do to the environment?

Pesticides kill bugs. That is good when the bugs do damage to crops.
Pesticides also kill good bugs by accident. That is bad when those bugs pollinate our food crops.
Pesticides are poisonous to other animals, such as pets and humans.
Pesticides run off into the water supply and kill fish.

Its more complicated than you think. The pesticides are toxic. There fore they kill bugs. But actually they are damaging the environment and creating more bugs resistant to pesticides. Some are already naturally resistant and some adapt and evolve to be resistant. The bugs are sprayed on by the pesticides, but there are a few naturally resistant bugs that survive. Since the spawn time of a bug is really short, the resistant buys mate and create more resistant bugs and ruin the crops. Then the farmers have to buy a different pesticide to kill the resistant ones and so on.
The pesticides are also not good for the plants. When the pesticides are put on, they don't become poisonous, but the plan absorb the pesticides and some of them lose the ability to reproduce.
Then some of the pesticide is washed away or absorbed into the ground. For one thing, pesticides are not good for people so people who don't wash their non organic food can get sick. Then like i already mentioned, the pesticides are washed away and absorbed. This causes the water with pesticides in them to wash away into a river and into the ocean. That kills many fish.
And thats not all. Other animals are being affected by this too. The mice and the crows that eat the crops are intoxicated. The crows would get sick and die. Not only the crows but the eagles and owls and hawks too. They eat the intoxicated mice. But since the birds eating the mice aren't fist to get the pesticides, the effects are different. Instead, their eggs lack calcium and grow very weak. If the eggs are weak, when the bids sit on them.. they break. One spices of eagle is on the edge of extinction because of this. This eagle is called the Golden eagle.
There is one more thing about pesticides (just make your essay longer). Because the bugs adapt to the pesticides, The companies have to produce more and more pesticides. That causes pollution  and more toxic gas. The toxic gas rises in the atmosphere and turns into the form of toxic rain. And the smog from the factories thin the ozone layer.
You need to do more research on what i gave you. But.. can I lease get best answer? I marked this question interesting and took a long time typing this out. I hope this helped!

Your topic is not very balanced, A better topic would be the pros and cons of pesticides.

Pesticides have saved 100's of millions of lives and improved the heath of countless more since there use began, while the harm they have done has be limited to a very small number compared to that.