By comparing species compositions in fixed plots along an elevational
gradient in Monteverde National Park, Costa Rica, Pounds et al. (1999, 2005) documented
that lowland birds have begun breeding in montane cloud-forest habitat over
the past 20 years. A similar study across 26 mountains in Switzerland documented
that alpine flora have expanded toward the summits since the plots were first censused
in the 1940s (Grabherr et al. 1994, Pauli et al. 1996). Upward movement of treelines
has been observed in Siberia (Moiseev & Shiyatov 2003) and in the Canadian Rocky
Mountains, where temperatures have risen by 1.5◦C (Luckman & Kavanagh 2000).