But that decline is slowest — and can sometimes be reversed — where humans are intervening in the landscape, according to findings published on Wednesday in the Journal of Applied Ecology.
The researchers studied more than a hundred populations of 31 at-risk butterfly species like the frosted elfin and Oregon silverspot across 10 U.S. states.
“In places where people are actively engaged with ways to manage the habitat, the butterflies are doing the best,” Washington State University biology professor and coauthor Cheryl Schultz said in a statement.
Schultz said that finding was particularly “exciting” because the effects of habitat management — from mowing and burning to control weeds to deliberately planting food and host species for caterpillars — could blunt many of the macro-scale effects of climate change.
These include the shifts in when plant and animal species reproduce, a dynamic which can push species disastrously out of sync with those they eat, shelter under or have their populations controlled by.
The bigger the shift in when plants bloom, the worse for butterflies, researchers found — and the greater the management a given tract received the smaller the climate-driven shifts in timing.
The researchers urged managers — including in home gardens — to plant a wide assortment of wildflowers and to avoid using pesticides.
The butterfly findings come out amid broader discoveries of the importance of human landscapes in ensuring the health of pollinator species.
A study published Wednesday in PLoS ONE revealed that the plant mix in a home garden was the most important factor in determining how diverse and abundant local pollinators were — far more than “the surrounding local or landscape context,” the authors wrote.
The biggest contributor to a greater number of bees — or variety of species — on a given property was a corresponding rise in the number of families of flowering plants on site, the authors found.
Gardens sown with flowering plants from three families — the Asteraceae (daisies), Fabaceae (legumes), or Lamiaceae (mints) — had far more pollinators on site and for 150 feet around than those planted with just one family, regardless of whether the site was in the midst of farmland, forest or grassland.
