When I had the greenhouses, I used Roundup a lot to control weeds out on the lots where I had plants displayed during warm weather. As for the amphibians? Frogs hatched out in the water puddles and toads frequented the perennial row.
My husband, who was first mine manager and then, after the mine closed, reclaimation foreman of a large strip mine (coal), also used a lot of it, as it was approved by the EPA. And let me tell you, the EPA watches the strip mines like a hawk, because of the run-off into public water supplies.
But after reading what BuckyTom said about Roundup, I thought I'd best check it out, as I wouldn't want to advise use of any dangerous chemicals in the garden, and since I've been out of the business for going on 8 years now, I figured there might be some new information out there...and there is.
First of all, here are the stats on the chemical...
glyphosate (Roundup) Chemical Profile
I then looked at this piece...
The Roundup Myth
What I get from this is that the surfactant (the ingredient that makes the chemical water soluable) was the culprit, so it must be used with one that is safe for wetlands. The strength of the mix is also a factor. If you use the pre-mixed stuff, both problems are eliminated.
Keep in mind that what we are talking about here are small controlled sprayings, not aerial application over large areas. Massive amounts of any kind of runoff can have ill effects, even fertilizer or cow manure.
For me, Roundup has been a valuable helper, and there have been no ill effects. The frogs still sing a chorus from the pond behind us, and I haven't seen any three-legged ones.