Monarchs on the rebound?

The past few years have been tough on monarch butterflies. Roundup, a widely used agricultural herbicide, kills the milkweed plants monarchs need for egg-laying. The late-summer migration from temperate zones to the mountains of central Mexico can be disrupted by severe September weather. And even after monarchs reach the relative safety of oyamel fir forests, winter storms can wreak havoc. The monarch population is down 90 percent over the past 20 years — they occupied just a single acre of habitat last winter. But monarch watchers reported encouraging news this summer. Midwest monarch numbers are up. Chip Taylor, director of Project Monarch Watch (www. monarchwatch.org), recently predicted “a modest increase in the number of monarchs in migration and at overwintering sites this winter.” Last year’s winter population was low, but they seemed to winter well. March and April in Texas were favorable for milkweed growth, and late-spring temperatures in the Southern plains helped first generation monarchs survive and move northward. Lincoln Brower, who began studying monarchs in 1954, prefers to wait until researchers visit Mexican wintering sites in December to evaluate the size of the overwintering population. “We know that monarch density averages about 20 million per acre on the wintering grounds, so after we determine how much winter habitat is occupied, we can more confidently estimate the size of the overwintering population,” he said in a recent interview. Conservationists led by the Center for Biological Diversity, the Xerces Society and Center for Food Safety are working to have monarchs listed as a threatened species.