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\begin{document}

\title{Swidden agriculture in transition and its roles in tropical forest loss
and plantations expansion}



\author[1]{Peng Li}%
\author[2]{Chiwei Xiao}%
\author[3]{Zhiming Feng}%
\affil[1]{Institute of Geographic Sciences and Natural Resources Research, CAS}%
\affil[2]{Institute of Geographic Sciences and Natural Resources Research CAS}%
\affil[3]{Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences}%


\vspace{-1em}



  
  \date{May 08, 2024}


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\selectlanguage{english}
\begin{abstract}
Tropical forest and swidden agriculture are declining, while commercial
plantation is continuously expanding. However, little is known about the
mechanisms, processes and trends of the tropical
forest-swidden-plantation (FSP) nexus. Global ongoing initiatives
including the UN-REDD Programme, not only have repeatedly emphasized the
significance of conserving forests, reforestation and afforestation, but
re-pushed swidden agriculture to the forefront of a long-standing
international debate of climate changes and biodiversity. Many facets
limit our understanding of swidden agriculture. The lack of geographic
and demographic data and their dynamics across the tropics undoubtedly
further aggravate this situation since the first appeal of eradication
of shifting cultivation by the FAO. Although recent studies have
enriched significantly our knowledge of forest loss and plantation
expansion, previous research has proceeded separately and has yet to be
integrated under the umbrella of sustainable swidden agriculture.
Efforts are needed to investigate the dynamics of the FSP nexus for sake
of a synergetic goal of climate mitigation and poverty alleviation.%
\end{abstract}%



\sloppy


\textbf{Swidden agriculture in transition and its roles in tropical
forest loss and plantations expansion}

\textbf{Abstract:} Tropical forest and swidden agriculture are
declining, while commercial plantation is continuously expanding.
However, little is known about the mechanisms, processes and trends of
the tropical forest-swidden-plantation (FSP) nexus. Global ongoing
initiatives including the UN-REDD Programme, not only have repeatedly
emphasized the significance of conserving forests, reforestation and
afforestation, but re-pushed swidden agriculture to the forefront of a
long-standing international debate of climate changes and biodiversity.
Many facets limit our understanding of swidden agriculture. The lack of
geographic and demographic data and their dynamics across the tropics
undoubtedly further aggravate this situation since the first appeal of
eradication of shifting cultivation by the FAO. Although recent studies
have enriched significantly our knowledge of forest loss and plantation
expansion, previous research has proceeded separately and has yet to be
integrated under the umbrella of sustainable swidden agriculture.
Efforts are needed to investigate the dynamics of the FSP nexus for sake
of a synergetic goal of climate mitigation and poverty
alleviation.\textbf{Keywords:} Swidden agriculture, tropical
agriculture-forest frontiers (TAFF), the forest-swidden-plantation (FSP)
nexus, REDD, evolution-transformation-expansion

\textbf{Introduction}

Swidden agriculture (also called slash-and-burn or shifting cultivation)
including the length of fallow period and its intensity is continuously
evolving or being transformed since the mid-20th century, however, it
remains a widespread but controversial farming practice and/or land use
category in tropical uplands (see the figure, panel \emph{A} )(Cairns,
2015; Heinimann et al., 2017; van Vliet et al., 2012). Sometimes, this
is a straw to clutch for millions of impoverished upland ethnic groups
facing constantly-changing market and extreme climates (e.g. El
Ni\selectlanguage{ngerman}ño)(Cramb et al., 2009; Smith \& Dressler, 2019). The evolution and/or
transformation not only matter the swidden-dependent uplanders, but also
trigger endless arguments (e.g. pros and cons) of swidden agriculture
towards carbon emission and biological diversity(Fox, Castella, \&
Ziegler, 2014). After age-long coexistence with human beings, how will
the traditional farming (or practice) develop in this century(Heinimann
et al., 2017)? Will it demise or persist?\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Forest-swidden-plantation in the tropics} . (\emph{A} ) Tropical
uplands (green parts) between 200 and 2000 m above sea level are defined
here as potential distribution regions of swidden agriculture (Part a).
Swiddens and fallows are reclaimed from natural and secondary forests in
the uplands of Mainland Southeast Asia (MSEA, \emph{B-E} ) and are being
converted to industrial plantations including rubber, cassava, sugarcane
and \emph{Acacia mangium} in Xishuangbanna, China and MSEA countries
(\emph{F-I} ).

Global ongoing initiatives, such as the United Nations Collaborative
Programme on Reducing Emissions from Deforestation and Forest
Degradation in Developing Countries (UN-REDD Programme)(Hurtley, 2010),
the Bonn Challenge(Brancalion et al., 2019) and the 2030 Sustainable
Development Goals (SDGs) etc., have repeatedly emphasized the
significance of forest preservation, reforestation and afforestation on
one hand, and re-pushed swidden agriculture, the traditional tropical
farming practice, to the forefront of a long-standing debate of climate
changes on the other(Hurtley, 2010; Ziegler, Fox, \& Xu, 2009). In the
past decades, the alternative development of swidden agriculture is
often considered as the ``only way out'' due to the threat to
forests(Ziegler et al., 2009). This is usually the case of pioneer
swiddening(Fox et al., 2000), but not for swidden agriculture as a
whole(Dressler, Smith, Kull, Carmenta, \& Pulhin, 2020). So far, less
attention is given to its significance to local livelihoods and cultural
identity of millions of marginalized shifting cultivators(Cramb et al.,
2009). As swidden farming evolves or being transformed, then, how did
swidden agriculture itself and the length of fallow period (or
intensity) change in the past decades? What are the roles in and
contribution to the gain and/or loss of natural and secondary forests by
the combination of swidden-fallow? And how are swiddens (including
fallows) transformed into other land use types, especially the various
industrial plantations (e.g. rubber)? Last but not least, how and in
what degree do global initiatives (e.g. the UN-REDD Programme) impact
the tropical forest-swidden-plantation (FSP) nexus?

\textbf{The uncertainties of the development of swidden agriculture and
its dynamics}

Many facets limit our understanding of swidden agriculture. The lack of
geographic and demographic data and information on their corresponding
dynamics across the tropical regions undoubtedly further aggravate the
uncertainties surrounding above questions(Heinimann et al., 2017; Mertz
\& Padoch et al., 2009; Padoch et al., 2007). Ever since the first
appeal of the eradication of shifting cultivation by the FAO in the late
1950s(FAO Staff, 1957), \emph{in situ} anthropological, ethno-ecological
and/or ethno-biological studies dominated for a long time(Brush, 1975).
The launch of Landsat satellites in the 1970s offers the feasibility and
marks the beginning of periodically observing this ancient farming
system(Conant \& Cary, 1977). However, research progress in the
algorithms for mapping swiddening or shifting cultivation is not
prominent, if not retarded or stagnant(Li, Feng, Jiang, Liao, \& Zhang,
2014). So far, the only thematic map of global shifting cultivation,
largely speculative and conspicuously old-fashioned, was firstly
reported in 1980(Hurtt et al., 2011), although a few new attempts have
emerged recently at regional scale, e.g. montane mainland Southeast
Asia(Li, Feng, Xiao, Boudmyxay, \& Liu, 2018; Li \& Feng, 2016). In
addition, the annually-changing and spatially-random dynamics of swidden
agriculture mean that it is seldom included in existing classification
maps of land cover and land use(Padoch et al., 2007), plus prevailing
governmental eradication policies. The report of shifting cultivation
maps in South and South East Asia, China, Africa, and South America
based on the SPOT-VGT based Global Land Cover 2000 (1km) can be consider
an early attempt via remote sensing at large scale(Silva, Carreiras,
Rosa, \& Pereira, 2011). However, the question about the accuracy of the
1km-resolution regional maps always persists as tropical swidden
agriculture belongs to small-scale farming systems with small-sized
plots (about 0.01km\textsuperscript{2})(Li et al., 2014). Even worse,
longitudinal dynamics of the evolution or transformation at a coarse
resolution increases greater uncertainty. Unsurprisingly, few studies
have been involved the spatiotemporal dynamics(Li et al., 2018). Lately,
the contributions of shifting agriculture and other four factors to
global deforestation were quantitatively for the first time(Curtis,
Slay, Harris, Tyukavina, \& Hansen, 2018). However, the fact that
shifting cultivation is still practiced in many extra-tropics regions
including Europe, North America, Australia, North China and many other
countries is problematic and unconvincing. Since shifting cultivation is
one of the main causes of tropical active fires(Cochrane, 2003; Li,
Xiao, Feng, Li, \& Zhang, 2020) and shifting cultivators are typically
poor ethnic minorities in remote uplands with limited
accessibility(Mertz \& Leisz et al., 2009), the estimation of greenhouse
gas emissions and achievement of the SDGs will be impacted without
accurate figures and maps for the land coverage of swidden agriculture.

Shifting agriculture as well as commodity production, forestry and
wildfire are the leading drivers of global forest loss(Curtis et al.,
2018). Among them, the first two were preeminent in tropical regions
particularly in the past two decades, which are always accompanied by
frequent fire occurrence or biomass burning especially during the dry
season. Anthropogenic fires not only occur in tropical upland and
lowland agriculture, but also in tropical agriculture-forest frontiers
(TAFF)(Li et al., 2020). In the uplands, vegetation fires are generally
related to traditional practice of slash and burn(Cochrane, 2003), which
acts as a key part of swidden agriculture. In the past, the words of
``slash and burn'' meant primitive and backward, or the stumbling block
of national economic development. By the same token, the
overgeneralization of describing swidden system as old as the hills
could make us bet on the wrong horse(Pham Thu, Moeliono, Wong,
Brockhaus, \& Dung, 2020). Conversely, this becomes more necessary as
increasing evidence are connected with social and ecological outcomes of
this farming system(Downey, Gerkey, \& Scaggs, 2020; Ziegler et al.,
2012). The positive effects of swidden agriculture are gaining ample and
convincing evidence in the aspects of carbon fixation, biodiversity
maintenance, livelihoods risk and cultural identity(Dressler et al.,
2020). Then, why should we still stick to the one-sided views of swidden
systems?

\textbf{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 \emph{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.

\textbf{Conclusions}

Although swidden agriculture has long been at the center of the debates
over climate change and biodiversity, it remains an essential livelihood
source for hunter-gatherers and become an increasingly important farming
system for global ongoing initiatives. Global rising demand of food,
commodities and bio-energy by a growing population have telecoupling
effects on tropical commercial plantation expansion. Meanwhile, land
scarcity and loss due to dispossession and grabbing in the name of
forest conservation and development diminish swiddening practices and
shorten fallow cycles, which undermine the sustainability of swidden
agriculture in this century. In view of the importance and research
status of swidden agriculture, we proposed the framework of
forest-swidden-plantation (FSP) nexus in the tropics and highlighted the
processes, mechanisms, scenarios of the dynamics of the FSP nexus on one
hand, and to promote the sustainable development of swidden agriculture
for sake of a synergetic goal of global climate mitigation and tropical
poverty alleviation on the other hand.

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