Geoscience Reference
In-Depth Information
Figure 5.18 Map of Asian seasonal forests.
(Map by Bernd Kuennecke.)
islands of the East Malesian subregion evolved their own distinctive flora and
fauna found nowhere else on Earth. When the Australian plate moved northward
and collided with the Asian continent (about 30-20 mya), dispersal of Asian spe-
cies into the area was made possible, and the subregion became a mix of species
from the two subregions. Some distinctive differences in the flora and fauna remain
between the subregions. Wallace's Line between Borneo (Kalimantan) and Sula-
wesi (Celebes), and Bali and Lombok farther south, defines the end of the Sunda
Shelf, a shallow extension of the continental plate under most of Indonesia. The
deep trench at the end of the shelf has been a significant barrier to species dispersal,
keeping species (particularly mammals) distinctive and separate. Fluctuations in
sea level in the past exposed land bridges, allowing some exchange of species
among islands. Today, plants and animals are transported throughout the region
intentionally and unintentionally by humans. Aggressive invasive species have
begun to dominate in certain areas, threatening many species and habitats.
Climate
The climate throughout the Asian-Pacific seasonal forests is significantly influenced
by monsoonal cycles. Monsoons are seasonal shifts in wind directions in which
moisture-laden air moves from ocean to land during the summer, and drier air
moves from land to sea in the winter. Most of Southeast Asia, including the main-
land, experiences a seasonal monsoon climate with a wet summer and dry winter.
