Indexing Endangered Species Risk in the Colorado River Delta, Mexico Using AVHRR NDVI Time Series Data

Abstract

The Colorado River Delta in Mexico has several U.S. listed Endangered Species. Methods that estimate the risks of hydrologic disruption would help protect the habitat of these animals, especially in remote areas like the Delta, where ecosystem and water availability monitoring does not occur. A Delta Response Index (DRI) was developed using NOAA Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) time series data. AVHRR NDVI data from a flood‐fed wetland (Rio Hardy) and an agricultural run‐off fed wetland (Cienega de Santa Clara) in Colorado River Delta in Mexico were used to develop the DRI. Analysis of the DRI in the Colorado River Delta since 1989 demonstrates the impact of floodwaters on the habitat of Delta endangered species, such as the Yuma clapper rail (Rallus longirostris yumanensis) and desert pupfish (Cyprinodon macularius). This finding may have significant environmental policy implications by removing Mexico as a potential intervening party between US fresh water releases and delivery to the Delta, and is relevant to current legal actions over Endangered Species Act (ESA) enforcement in Mexico.