Digital Data for Land and climate change in Mexico and Texas reveals small effects on migratory habitat of monarch butterflies (Danaus plexippus).

The decline of the iconic monarch butterfly in North America has motivated research on the impacts of land use and land cover (LULC) change and climate variability on monarch habitat and population dynamics. We investigated spring and fall trends in LULC, milkweed and nectar resources over a 20-year period, and ~30 years of climate variables in Mexico and Texas, a key region supporting spring and fall migration during monarchs annual life cycle. We estimated a 2.9% decline in milkweed in Texas, but little to no change in Mexico. Fall and spring nectar resources declined <1% in both countries. Vegetation greenness increased in both the fall and spring in Mexico while the other climate variables, for both countries, did not. Monarch habitat in Mexico and Texas appears relatively more intact than in other parts of their range, particularly the midwestern agricultural landscapes of the US. Given the relatively modest observed changes, it seems unlikely that habitat loss (quantity and quality) in Mexico and Texas has caused large declines in population size or survival during migration.