The Future of Peary Caribou (Rangifer tarandus pearyi) in a Changing Climate

In the last half century, trends in mean temperature (increasing), snowfall (increasing), and snow cover (decreasing) that are consistent with global warming predictions have been observed in the Arctic (Brown and Alt 2001; Gitay et al. 2002; Whitfield et al. 2002). Additionally, climate variability in the Arctic has increased: there has been a significant increase in the number of thaw days in autumn and winter (Groisman et al. 2003) and an increase in the frequency of heavy precipitation events (Gitay et al. 2002). These changes confirm reports by Inuit of climate warming and associated ecological changes (Nunavut Tusaavut Inc. 1997; Ashford and Castleden 2001). Over roughly the same period, 1961–2001, Peary caribou (Rangifer tarandus pearyi) populations have declined by 84% (Harding 2003). Several of the declines have resulted from winter die-offs when > 90% of the caribou, as well as muskoxen, died of starvation during severe winter conditions of deep, hard-packed, or frozen snow that prevented access to forage. This has led to speculation that climate change has caused the observed four-decade overall decline in the subspecies (Miller 1991; Ferguson 1996; Gunn 1998; Miller and Gunn 2003b). The declines, however, have been spatially and temporally inconsistent among the various Peary caribou populations: some populations have increased while others have decreased. Additionally, at least two of the die-offs preceded the period of observed global warming. Moreover, postulating a caribou decline because of global warming seems counter-intuitive: the extensive high latitude warming and associated cryosphere changes (e.g., longer snowand ice-free seasons) that have been documented in the northern hemisphere in recent decades, consistent with predictions of greenhouse gas-forced global warming (Zhang et al. 2000; Brown and Alt 2001; Whitfield et al. 2002), should improve survival, not lessen it. Therefore, a review of the hypothesized connection between Peary caribou populations and climate change is warranted.