Sevilleta LTER

Correlating Long-term Climate Trends with Hantavirus Outbreaks in the Southwest U.S.

The long-term studies of rodent populations an the Sevilleta LTER site have proved valuable in unraveling elements of the outbreak of Hantavirus. Initially identified in the southwestern U.S. in the spring of 1993, scientists at the Federal Centers for Disease Control and Prevention (CDC) enlisted the aid of Sevilleta scientists in identifying ecological aspects of the epidemic of Hantavirus Pulmonary Syndrome, which had resulted in dozens of deaths. Serological tests of rodents in the region revealed the virus in several species. The Sevilleta data showed large population increases in the critical rodent species (Peromyscus spp.) during 1992 and early 1993. Comparison of the rodent data to regional climate data indicated that the rodent population dynamics were positively associated with the above-average precipitation during the 1992 El Nino and the mild winter of 1992-1993, which led to increased ecosystem productivity and subsequent rodent population explosions . These data provided a causal mechanism for the epidemic's timing and spatial distribution in the Southwest.

Results of the Sevilleta analyses were used to develop rodent/virus sampling strategies, models to predict potential disease outbreaks, and disease prevention plans for human populations. Additional studies have advanced techniques for measuring long-term changes in rodent populations, and have been useful for predicting a second hantavirus outbreak (CDC 1998) (Yates, et al. 2002). Finally, with NIH funding, the Sevilleta NWR has become the site of two major hantavirus programs utilizing large rodent enclosures to examine the ecology of hantavirus transmission in wild rodent populations.

In addition to research on Hantavirus, predictive models have been constructed to provide early warnings of environmental conditions in which bubonic plague outbreaks may occur.

Long-term Climate Data indicate drought cycles in southwestern U.S.

Findings useful for regional water planning

Sevilleta scientists have collaborated with Drs. Julio Betancourt (USGS, Tucson, AZ) and Thomas Swetnam (U. Arizona Tree Ring Laboratory), on the development of historical climate, fire, and floristic records for the Sevilleta region based on tree ring analyses and pack-rat middens. Recent results of these studies have led to an understanding of the impact of severe drought, leading us to simulate how climatic fluctuations may affect ecosystem structure and functioning (Swetnam and Betancourt 1998).

Additional insights on these precipitation records gleaned from tree ring data on the Sevilleta over the last 700 years have revealed a cycle of ~60 yr between severe, decade-long drought periods; given that the most recent recorded decade-long drought occurred in the 1950s, the next predicted drought in the Southwest should begin within the next 10 years. These results are now being provided to land managers and political leaders for incorporation into long-term water use plans in the Rio Grande Basin.