How effective is putting chicken wire around trees to protect against beavers?
Chicken wire is certainly more effective than doing nothing—and, compared to other beaver-deterring options, it’s probably one of the fastest, easiest, and least costly to implement. But chicken wire is flimsy (and intended for, well, chickens), so, depending on how many layers you use and how you’ve wrapped the tree, it may not stand up to a beaver assault. They could pull it down and crush it. A heavier welded wire tree “cage” may be a better choice if you’re going to protect a few individual trees (other alternatives are hardware cloth or sheet metal). Make these wire cylinders about a metre high. Since beavers aren’t great climbers, a 1.5 m fence can work as a permanent deterrent around stands of trees.
You can also try discouraging the beavers by spraying the trees with a repellent such as Ropel (it makes the trees taste bitter), or by painting them with sand; the Ontario Ministry of Natural Resources recommends 120 ml of masonry-grade sand for every litre of latex paint. Of course, you’ll probably have to keep re-applying these treatments, and this won’t necessarily make the beavers abandon your property—it may just drive them to go after different trees, shrubs, or ornamental plants.