Probably the easiest and most impactful thing is keeping cats indoors and encouraging friends and neighbours to do the same.
Outdoor cats are absolutely disastrous for birds and small mammals.
https://www.smithsonianmag.com/science-nature/moral-cost-of-cats-180960505/
@BathysphereHat after that, contributing money to conservation non-profits, making political contributions, writing letters, and keeping native plants in your garden.
@BathysphereHat after *that*, I'd say reducing red meat, since cows and sheep and pigs take up a lot of space that could be used for wildlife preserves.
Anyways, there's a lot an individual can do.
@BathysphereHat get a load of Mr. I-Don't-Answer-Clarifying-Questions