Phenological variation and greening of the Monarch Butterfly Biosphere Reserve (2000-2019)

Introduction: The Abies forest of the Monarch Butterfly Biosphere Reserve (MBBR) is a key ecosystem for the butterfly Danaus plexippus L. The study of this habitat is essential to understand the global effects of environmental transformation. Objectives: To study the impact of climate change over the last 20 years (2000-2019) on the MBBR, to (1) describe variations in climate and phenology; (2) analyze the relationships between LAI (leaf area index) and climate; and (3) estimate greening Materials and methods: Monthly mean temperature and precipitation values from the NASA Giovanni database and the Copernicus LAI series were analyzed. Using the TIMESAT algorithm, 11 phenological variables per pixel and year were determined and the annual spatial average of each one was calculated for each type of land cover (pine, oyamel, shrubs and crops) and the cumulative increase of the extended integral (greening). Results and discussion: Mean temperature increased 0.87 °C in 2000-2019. Beginning, middle, and end of the season have occurred progressively earlier, and cumulative leaf area, as well as minimum and maximum LAI, have increased. Greening was recorded in 53.21 % of the MBBR and browning in 33.97 %. Conclusion: The increase in mean temperature affects phenology of MBBR, causing longer growing seasons and net greening of the area.