many countries in the tropical belt of the globe,
forests are in transition. These forests, which until
now were cut at a sometimes alarming rate, recently
begun to regenerate.
Forests in transition are
relatively complex landscapes with alternating patches
of intact forest, clear cutting and forest patches
in various stages of degradation and regeneration.
These forests in transition, with their heterogeneous
landscape, are of great importance to a number of
ecological parameters, such as biodiversity, conservation
of soil and water resources and carbon sequestration.
This process of forest transition
takes place in response to two types of situations:
- when the economic development
of a country creates enough employment in sectors
beside agriculture. In this case farmers abandon
their lands and fields, and leave them be, whereafter
they are gradually recolonized by the forest;
- when governments or landowners
decide to plant trees in abandoned fields. This
can be encouraged by lack of certain forest resources
or by international mechanisms for compensation
under environmental legislation. An example of these
mechanisms is the REDD (Reducing Emissions from
Deforestation and forest degradation), which aims
to encourage countries to preserve their rainforests.
Its principle is to offer financial compensation
to developing countries, that avoid or reduce deforestation,
to cover the corresponding financial losses .
Recent research has shown
that sometimes the regeneration of the forest in an
area leads to deforestation elsewhere. It is therefore
useful to observe the transitions at landscape scale,
so as to demonstrate the potential negative effects
of forest preservation, due to a higher pressure on
other types of land use.
The changes in forest
cover can be monitored using various types of remote
sensing data. High-resolution data are used to detect
changes in forest cover at the local level. Low-resolution
time series data complement the analysis at the regional
level. The same low-resolution data can be used to
identify changes in productivity.