Theo and JHAP, I somewhat agree with your statement that I have already started man-made selection by changing the landscape during construction of the pond. But I also disagree.
It's so damn hard to get a consensus from all three stooges.
I want to say that we added improvements to their environment by adding the pond, but now that I think about it, maybe the pond drew in new species that might provide new pressure on the species that safely resided there without the water magnet. hmmmmm......
HA! Made you think.
When I look out over our pond and see the fish swirling at the surface, hear the call of a bull frog, watch a dragon fly perch on a nearby reed, I realize that our pond provides a place for life to flourish. Did I alter the existing ecosystem? (No actually the pond was there already, so unlike Brettski, I'm not a mass murderer.

Sorry Bski, I'm just practicing up on my guilt skills).
I'll bet in the long run you provided a habitat that will give more life than the life that will be taken away in order to ensure the viability of Liberty Nature Preserve.