In recent decades, the monarch population has suffered a sharp decline—some estimates put it at 90 percent—and the loss of milkweed is mainly responsible. Milkweed, the only plant on which monarchs will lay eggs, started to wither after the introduction of herbicide-tolerant crops in the 1990s. The resulting spike in herbicide use all but wiped out the attractive perennial, whose blossoms provide nectar for a dozen species of butterflies and moths.

Fortunately, milkweed remains abundant at Balcones Canyonlands—a 33,000-acre sweep of Ashe juniper forests and limestone canyons northwest of Austin. In the past 25 years, Trust for Public Land has added more than 3,000 acres to the wildlife refuge.

Trust for Public Land has protected forests, farmland, mountains, and meadows across the country, including many places with excellent butterfly habitats.