Conclusions
If it does not replace natural vegetation but rather is established in already-
deforested lands, agroforestry has the potential to benefit fragmented popula-
tions and ecosystems in several ways. First, it is apparent that creating dense,
tall-statured vegetation near the margins of forest fragments can reduce many
of the deleterious edge effects discussed in this chapter (Gehlhausen et al.
2000). Forest fragments surrounded by tree plantations or agroforestry are
likely to suffer far less severe alterations in microclimate and less wind turbu-
lence than do fragments encircled by cattle pastures or herbaceous crops.
Given the obvious importance of edge effects in fragmented tropical land-
scapes, reducing the intensity of such effects could be a major benefit of
enlightened agroforestry practices.
Second, agroforestry methods have the potential to increase fragment
connectivity and species survival, especially if used in concert with land-
scape design principles such as corridor systems (see Chapter 3, this vol-
ume). Forest-dependent animals are much more likely to traverse modified
lands that contain substantial tree cover than areas that have been denuded
of trees (Laurance and Bierregaard 1997). Nevertheless, the most vulnera-
ble species in fragmented landscapes often avoid modified habitats alto-
gether (Laurance 1991a; Gascon et al. 1999; Laurance and Laurance
1999), and for these species the potential benefits of agroforestry may be
limited.
Third, under some circumstances agroforestry can be used to provide food
or shelter for fragmented wildlife populations. In tropical Queensland, Aus-
tralia, the use of “framework” tree species that attract a wide variety of frugiv-
orous birds and bats has been advocated as a strategy for landscape restoration
(Lamb et al. 1997). These mobile frugivores deposit the seeds of many other
plant species beneath the planted trees, accelerating the process of forest regen-
eration. Likewise, almost all tropical forests experience strong seasonal or
interannual declines in fruit availability (Terborgh 1986; Wright et al. 1999).
These declines can cause severe famines in fragmented populations (Van Shaik
et al. 1993; Wright et al. 1999), which are unable to migrate to areas with
greater fruit abundance. The provision of plants near fragments that have con-
tinuous fruit crops, such as figs (Ficusspp.) and many palms, or that repro-
duce during periods of annual fruit scarcity could have important benefits for
fragmented wildlife populations.
A final and obvious benefit of agroforestry is that it reduces the use of fire.
Fires are anathema to farmers who rely on perennial plants such as fruit trees
and timber plantations. Given the striking vulnerability of fragmented forests
to fire, the reduction of burning may be one of the most important environ-
mental benefits of agroforestry systems in the tropics.
- Ecological Effects of Habitat Fragmentation in the Tropics 43