Tropical Deforestation
The world's tropical forests disappeared at the rate of 15 million hectares per year (equivalent to 40 percent of the Japanese archipelago) during the latter half of the twentieth century. Tropical forest ecosystems contain the world's greatest diversity of flora and fauna. The rapid loss of forest area affects not only timber but also genetic resources, and it may also lead to a loss of carbon sequestration potential.
Causes of Tropical Deforestation
The background of deforestation varies from place to place
in the tropics, but is mainly attributed to clearcutting to create agricultural
land. In Southeast Asia, timber is extracted by a selective logging system,
in which only the commercially merchantable timbers are selected for felling.
Therefore, the logging operation itself does not necessarily lead to the
pronounced reduction of forest coverage. However, even such selective
logging has been shown to cause some impacts on the forest structure,
biodiversity, hydrology, microclimate and carbon storage functions of
the forests. On the other hand, when one considers that almost all tropical
deforestation occurring in Southeast Asia is caused by large-scale conversion
to agriculture, it is important to quantify ecological the service value
of virgin and regenerating forests in comparison to other types of land
use.
Initiatives by NIES
Collaborating with research institutes in Japan and Malaysia,
including the Forestry and Forest Products Research Institute of Japan
(FFPRI), the Forest Research Institute Malaysia (FRIM), and the University
Putra Malaysia (UPM), NIES is conducting research on the following topics
to investigate how the ecological functions of old growth rainforests
are altered as a result of logging:
View
of canopy of tropical rainforest from the top (52 meters) of observation
tower set up in Pasoh Forest Reserve, Malaysia
- Forest canopy, stand structure and species composition
- Regeneration processes of tree communities
- Species composition of insects and mammals
- Plant and animal interactions and their role in maintaining biodiversity
- Carbon sequestration potential and forest microclimates
- Hydrological aspects of forests
- Socio-economic and recreational values of forests
Impacts of Selective Logging on Forest Structure and Wildlife
We studied the impacts of selective logging on a tropical rain forest
in Peninsular Malaysia, by comparing the canopy and stand structure, as
well as tree and animal species composition between areas consisting of
unlogged primary forest and regenerating forest that had been logged in
the 1950s. The studies found that canopy height, canopy surface area and
crown size of canopy trees were all reduced by logging. Emergent trees
(less than 40 meters in height) were hardly seen in the regenerating forest.
Stem densities and basal areas were similar between the two forests, but
the stem density per hectare and basal area of small- to medium-sized
trees (less than 30 cm in diameter) were significantly higher in the regenerating
forest.
Changes
in primary forest structure after logging
These results imply that gap formation and structural development take a long time to manifest in a regenerating forest as a result of the time taken for self-thinning to begin. Monotonic canopy structure also resulted in changes in the composition of insects and mammal species; population densities of animals associated with multi-layer canopy structure were reduced. Termites, which depend on the food in the canopy trees, were also lower in density. Forest fragmentation as a result of logging or clearcutting, induced the density of frugivorous birds, but reduced that of insectivorous birds.
Ecological Service Value of Tropical Forests and Landscape Management
The quantification of the ecological service value of forests is urgently needed in order to implement the sustainable management of tropical forests. This quantification will allow the creation of model plans to optimize the benefits but minimize the risks of ecological impacts, resulting in the optimal landscape profiles. For this purpose, NIES is conducting a pilot survey to evaluate the socio-economic value of tropical forests in comparison to agricultural landscapes. Based upon these analyses together with other information related to ecological service value, we will estimate how the total economic value of each landscape unit varies depending upon the management scheme. For this purpose, we are now establishing geographic information systems data of a pilot area which will help visualize the management options. Besides these activities, we are also exploring the possibility of establishing green corridors which will enable wildlife to migrate between the fragmented patches in mixed landscape units consisting of virgin forest, forests regenerating after logging, and plantation regimes. As a part of this project, a silvicultural experiment was conducted to test the physiological performance of some tree species in relation to the local microenvironment.
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