Australia built a fence 5,614 kilometres long to keep dingoes out. It went up in the 1880s to protect sheep and runs from Queensland to the cliffs above the Great Australian Bight — the longest fence on Earth.
From orbit you can tell which side you are looking at, and the fence is the smaller clue. The ground is a different colour.
UNSW researchers pulled 32 years of NASA satellite imagery along the line. The two sides respond to rain differently: after the same storm, vegetation on the dingo side grows more and covers more ground. Rainfall and land use differ across the line too, and the researchers still found the dingoes central.
The mechanism runs downhill from there. No dingoes means no check on kangaroos. Kangaroo numbers climb, grazing pressure climbs with them, and the land thins — a trophic cascade running the length of a continent.
They fixed the sheep problem. They got the whole landscape instead.
Every fence keeps out more than the thing it was built for.