Central Park Ecological Conservation II: Assessing Drought and Vegetation Health Conditions in New York City’s Central Park with Earth Observation Data

With over 42 million visitors annually, New York City’s Central Park serves as a vital refuge from city life. Yet
as climate change accelerates, the park faces increasing challenges from extreme heat and droughts. This study explores how NASA Earth observations can detect drought-induced vegetation stress during a long-term drought in 2002 and a short-term drought in fall 2024. We used Landsat 5 TM, Landsat 7 ETM+,
Harmonized Landsat Sentinel-2, and ECOSTRESS environmental indices to assess vegetation stress across
lawns, ballfields, and woodlands. Four indices were calculated to measure vegetation health, moisture, and
evapotranspiration: Normalized Difference Vegetation Index (NDVI), Red Edge Normalized Difference
Vegetation Index (ReNDVI), Moisture Stress Index (MSI), and Evaporative Stress Index (ESI). Percent
change for a given index was calculated between drought year and historical baseline values. In the 2002
drought, woodlands were most stable while lawns and ballfields showed the largest declines in vegetative
health indicators. By summer 2003, most park areas returned to or exceeded baseline conditions. In 2024,
widespread negative percent change occurred in terms of foliar greenness and moistness, except in patches of the Sheep Meadow and Great Lawn. ReNDVI was particularly sensitive in the Ramble and North Woods,
with time series showing senescence two weeks earlier than normal. By spring and summer of 2025, lawns
and ballfields rebounded, though patches of the Ramble, Mall, Conservatory Water, and West Pinetum still
lagged in terms of showing normal values. Limitations included sparse baseline data and confounding effects
of fall senescence and management practices. Overall, this study demonstrates the feasibility of using NASA
Earth observations to detect drought stress in Central Park, informing irrigation and vegetation management.