10. Patterns of Terrestrial Vertebrate Diversity in
New World Temperate Rainforests
Peter L. Meserve
Temperate rainforests occur on the western margins of North and South
America between approximately 40
0 - 6 00
N-S latitude. These occur
primarily in the Pacific Northwest region of the United States and Canada
and in southern Chile, with extensions into neighboring precordilleran
Argentina. The climate of these regions is characterized by high, predominantly winter precipitation as rain and/or snow, averaging 1500mm to
3000mm or more annually, and mild maritime conditions. Depending on
whether the forests are perhumid or seasonal , summers may also be wet,
or relatively dry, but not hot. In both hemispheres, volcanism, orogenic
uplifts, and periodic Pleistocene glaciations have played a major role in
shaping the modern landscape . The southern temperate forest region has
also been affected by marine transgressions, particularly in the early and
mid-Cenozoic. Today , the temperate forests of both regions are essentially
isolated from coterminous regions by high mountain ranges (the Cascades
and Rocky Mountains, for North America, and the Andes, for South
America) that produce significant rainshadows to the east and, at the
same time, ameliorate conditions to the west. As recently as the Pliocene,
the southern temperate forests were much more extensive than at present,
extending east through much of what is now semiarid Patagonian steppes.
Forest vegetation may have also extended northward during glacial
maxima, occupying the area now dominated by Mediterranean scrub or
matorral (Vuilleumier, 1985; but see Markgraf, 1991, and Markgraf et
214
New World Temperate Rainforests
Peter L. Meserve
Temperate rainforests occur on the western margins of North and South
America between approximately 40
0 - 6 00
N-S latitude. These occur
primarily in the Pacific Northwest region of the United States and Canada
and in southern Chile, with extensions into neighboring precordilleran
Argentina. The climate of these regions is characterized by high, predominantly winter precipitation as rain and/or snow, averaging 1500mm to
3000mm or more annually, and mild maritime conditions. Depending on
whether the forests are perhumid or seasonal , summers may also be wet,
or relatively dry, but not hot. In both hemispheres, volcanism, orogenic
uplifts, and periodic Pleistocene glaciations have played a major role in
shaping the modern landscape . The southern temperate forest region has
also been affected by marine transgressions, particularly in the early and
mid-Cenozoic. Today , the temperate forests of both regions are essentially
isolated from coterminous regions by high mountain ranges (the Cascades
and Rocky Mountains, for North America, and the Andes, for South
America) that produce significant rainshadows to the east and, at the
same time, ameliorate conditions to the west. As recently as the Pliocene,
the southern temperate forests were much more extensive than at present,
extending east through much of what is now semiarid Patagonian steppes.
Forest vegetation may have also extended northward during glacial
maxima, occupying the area now dominated by Mediterranean scrub or
matorral (Vuilleumier, 1985; but see Markgraf, 1991, and Markgraf et
214