have demonstrated that for intermediate rainfall regimes,
1 forests and savannas can
both occur in the same regions. Under these climatic conditions they represent
alternative stable states maintained by a positive feedback between fire and canopy
cover (Hirota et al. 2011; Staver et al. 2011b; Favier et al. 2012). These two
ecosystems are unique, highly biodiverse, and can provide multiple ecosystem
services that are directly related to their unique functioning (see Chaps. 7 and 10,
Vol. 1; Chaps. 5 and 6, Vol. 2).
Tropical forests harbor more than 60% of all known species (Laurance and
Useche 2009), are characterized by unique food webs and high endemism and
diversity (Malhi et al. 2014). Tropical forests are also critical for the global climate
system (Spracklen et al. 2018) as they represent one of the largest carbon sinks,
which constitutes 40–50% of terrestrial carbon stocks (Pan et al. 2011; Achard et al.
2014).
The Congo basin is the largest forest block in SSA in terms of size, and is the
world’s second largest behind the Amazon. However, tropical forests in SSA have
been heavily used for a very long time, and can hardly be considered as pristine
(Chap. 10, Vol. 1), see also Willis et al. (2004) and Roberts et al. (2017) for evidence
of human activity across the tropics, and Morin-Rivat et al. (2017) across central
Africa). At the same time, tropical forests are facing the new pressures of the
Anthropocene (Malhi et al. 2014), such as accelerated deforestation and forest
degradation due to slash-and-burn subsistence agriculture, and more recently conversion for cash crops (e.g., cocoa, hevea) production (Sonwa et al. 2011), among
many other pressures (IPBES 2018). Land use change, that is, the conversion of
forest land into another land use, is the most important threat for tropical forests
worldwide (Sala et al. 2000; Malhi et al. 2014; Kehoe et al. 2017), and in particular
for SSA (Aleman et al. 2016, 2017). Deforestation occurs particularly around big
cities, and along major road axes and rivers (Verhegghen et al. 2012), and is
expected to continue along such patterns in the near future (Laurance and Arrea
2017).
The logging industry is dominated by industrial scale operations, also
representing a major driver of forest fragmentation across central SSA (Laporte
et al. 2007). Timber production is of extreme importance for the national economies
in the region, with production forests spanning 180 million ha (De Wasseige et al.
2012) (Chap. 1, Vol. 1). However, timber production does not necessarily induce
land use change (Pan et al. 2013). Indeed, temporal changes in forest cover due to
forest exploitation do not imply a conversion to another land use due to the quick
recovery of tropical forests after disturbance (Poorter et al. 2016) or silvicultural
interventions (Gourlet-Fleury et al. 2013). Moreover, forest management in central
SSA is highly selective with only few trees per hectare extracted over 25–30 year
rotations (Ruiz Pérez et al. 2005). This allows for the maintenance of a permanent
forest cover after logging, and offers the possibility to manage forests for timber
1 Intermediate rainfall regimes are 1000–2000 mm for SSA (Staver et al. 2011a) and 1000–2500 mm
for the global tropics (Staver et al. 2011b).
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J. C. Aleman and A. Fayolle
1 forests and savannas can
both occur in the same regions. Under these climatic conditions they represent
alternative stable states maintained by a positive feedback between fire and canopy
cover (Hirota et al. 2011; Staver et al. 2011b; Favier et al. 2012). These two
ecosystems are unique, highly biodiverse, and can provide multiple ecosystem
services that are directly related to their unique functioning (see Chaps. 7 and 10,
Vol. 1; Chaps. 5 and 6, Vol. 2).
Tropical forests harbor more than 60% of all known species (Laurance and
Useche 2009), are characterized by unique food webs and high endemism and
diversity (Malhi et al. 2014). Tropical forests are also critical for the global climate
system (Spracklen et al. 2018) as they represent one of the largest carbon sinks,
which constitutes 40–50% of terrestrial carbon stocks (Pan et al. 2011; Achard et al.
2014).
The Congo basin is the largest forest block in SSA in terms of size, and is the
world’s second largest behind the Amazon. However, tropical forests in SSA have
been heavily used for a very long time, and can hardly be considered as pristine
(Chap. 10, Vol. 1), see also Willis et al. (2004) and Roberts et al. (2017) for evidence
of human activity across the tropics, and Morin-Rivat et al. (2017) across central
Africa). At the same time, tropical forests are facing the new pressures of the
Anthropocene (Malhi et al. 2014), such as accelerated deforestation and forest
degradation due to slash-and-burn subsistence agriculture, and more recently conversion for cash crops (e.g., cocoa, hevea) production (Sonwa et al. 2011), among
many other pressures (IPBES 2018). Land use change, that is, the conversion of
forest land into another land use, is the most important threat for tropical forests
worldwide (Sala et al. 2000; Malhi et al. 2014; Kehoe et al. 2017), and in particular
for SSA (Aleman et al. 2016, 2017). Deforestation occurs particularly around big
cities, and along major road axes and rivers (Verhegghen et al. 2012), and is
expected to continue along such patterns in the near future (Laurance and Arrea
2017).
The logging industry is dominated by industrial scale operations, also
representing a major driver of forest fragmentation across central SSA (Laporte
et al. 2007). Timber production is of extreme importance for the national economies
in the region, with production forests spanning 180 million ha (De Wasseige et al.
2012) (Chap. 1, Vol. 1). However, timber production does not necessarily induce
land use change (Pan et al. 2013). Indeed, temporal changes in forest cover due to
forest exploitation do not imply a conversion to another land use due to the quick
recovery of tropical forests after disturbance (Poorter et al. 2016) or silvicultural
interventions (Gourlet-Fleury et al. 2013). Moreover, forest management in central
SSA is highly selective with only few trees per hectare extracted over 25–30 year
rotations (Ruiz Pérez et al. 2005). This allows for the maintenance of a permanent
forest cover after logging, and offers the possibility to manage forests for timber
1 Intermediate rainfall regimes are 1000–2000 mm for SSA (Staver et al. 2011a) and 1000–2500 mm
for the global tropics (Staver et al. 2011b).
282
J. C. Aleman and A. Fayolle