it is great that you want to help the enviornment! i think there should be a balance of each. like you said, cats impact the enviornment with their litter, which clogs up landfills. dogs impact the enviornment by needing wood for fences, urinating on plants, and infesting your water. both types of animals impact the land in different ways, so there should be an even number of each in your area. you say there a lot of dog owners where you live, right? well what about the cat population? if there is very few cats in your area, i would get a cat, that way the negative impacts on your water and plants aren't as servere. also, they have made new biodegradalbe cat litter. check out this very helpful website!!!!! http://www.worldsbestcatlitter.com/Products/WBCL/default.aspx. i think you should get a cat. they are easy to take care of and with the biodegradable cat litter they are safer fer the enviornment! check out that site. it is very helpful!!! hope i've convinced you!!! hope this helps!!!
i love helping the enviornment whenever i can and i have 6 cats............that is how i know this stuff.