The forest-swidden-plantation (FSP) nexus in the tropics
First, there is a need to carry out a synergic analysis of the tropical
forest-swidden-plantation (FSP) nexus more than at any time in history
under the context of rapid deforestation. The FSP nexus integrates both
natural/secondary forest and commercial plantation as the anterior and
posterior ends with swidden agriculture (also swiddening practice) as
the main thread. This integration contributes to understand the
self-evolution of swidden agriculture (including fallow period and
intensity), and also is helpful to investigate its corresponding roles
in natural forest changes (gain or loss) and expansion of tropical
plantation(Ziegler et al., 2009), such as tree crops (e.g. rubber,
coffee, and pulp trees) and non-tree crops (e.g. banana, pineapple and
sugarcane). Although recent studies have enriched significantly our
knowledge of forest loss(Curtis et al., 2018; Hansen et al., 2013) and
plantation expansion(Peltzer, Bellingham, Dickie, & Hulme, 2015;
Ziegler et al., 2009), the previous research has proceeded separately
and yet to be integrated under the umbrella of sustainable development
of swidden agriculture. In particular, much less is known about the
processes, mechanisms, and future trends of the interplays of natural
and secondary forests changes, swidden agriculture evolution and
transformation, and commercialized plantations expansion in the tropics
(see the figure, panel B-I ).
Second, there is a need to integrate remote sensing methods with more
traditional research. Consistent mapping of annual dynamics of swidden
agriculture (including fallow cycles) and cash crops plantation
facilitates tracking the advance trajectories of agricultural expansion
or forest loss (retreat) in TAFF. With the free access of satellite
imagery including Landsat and Sentinel-2, more efforts and new
algorithms are necessary to map and investigate the dynamics of
swidden-fallow trajectories, forest gain and/or loss, and plantation
expansion. People often question the data availability of optical
satellite imagery (e.g. Landsat) for mapping swidden agriculture and
rubber plantations in the tropics especially during the growth periods,
usually overlapping with the rainy season. However, this situation is
totally improved within a half-year dry season due to the tropical
monsoon climate(Li, Feng, & Xiao, 2018). Notably, the rotational and
commonly-used slash-and-burn phases (especially the signal of fire)
provide a key window for monitoring the transition from primary forest
to monoculture using phenology-based methods and/or machine learning
algorithms (e.g. random forest and neural network).
Finally, there is a need to understand the mechanisms through phenomena
of forest change (esp. deforestation), swidden transformation, fallow
period shortening, and plantation advance. Usually, the variation in
drivers and/or mechanisms of the FSP dynamics are huge in different
parts of the tropics. As for drivers of global deforestation, for
instance, there are agro-industrial crops, plantations (including oil
palm), pasture, small-scale clearing, selective logging, fire, and
infrastructure/natural disturbance(Seymour & Harris, 2019). Population
growth and migration, livelihoods diversity, markets and infrastructure
development, public policies and attitudes and other socio-cultural
drivers influence the persistence or demise of swidden agriculture(van
Vliet et al., 2012). Offsetting carbon, increasing bioeconomy demand,
urban migration, and government programs serve as the potential drivers
of tropical plantation expansion(Rudel, 2009). Geo-economic cooperation
mechanisms, national policies on land allocation, forestry, agriculture
and natural resources, and local (including household level)
agricultural practices are comprehensively needed to probe into the
mechanisms through a bottom-up inductive approach.