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- Morel, Alexandra C., et al.
(författare)
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Carbon dynamics, net primary productivity and human-appropriated net primary productivity across a forest–cocoa farm landscape in West Africa
- 2019
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 25:8, s. 2661-2677
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial net primary productivity (NPP) is an important metric of ecosystem functioning; however, there are little empirical data on the NPP of human-modified ecosystems, particularly smallholder, perennial crops like cocoa (Theobroma cacao), which are extensive across the tropics. Human-appropriated NPP (HANPP) is a measure of the proportion of a natural system's NPP that has either been reduced through land-use change or harvested directly and, previously, has been calculated to estimate the scale of the human impact on the biosphere. Additionally, human modification can create shifts in NPP allocation and decomposition, with concomitant impacts on the carbon cycle. This study presents the results of 3 years of intensive monitoring of forest and smallholder cocoa farms across disturbance, management intensity, distance from forest and farm age gradients. We measured among the highest reported NPP values in tropical forest, 17.57 ± 2.1 and 17.7 ± 1.6 Mg C ha−1 year−1 for intact and logged forest, respectively; however, the average NPP of cocoa farms was still higher, 18.8 ± 2.5 Mg C ha−1 year−1, which we found was driven by cocoa pod production. We found a dramatic shift in litterfall residence times, where cocoa leaves decomposed more slowly than forest leaves and shade tree litterfall decomposed considerably faster, indicating significant changes in rates of nutrient cycling. The average HANPP value for all cocoa farms was 2.1 ± 1.1 Mg C ha−1 year−1; however, depending on the density of shade trees, it ranged from −4.6 to 5.2 Mg C ha−1 year−1. Therefore, rather than being related to cocoa yield, HANPP was reduced by maintaining higher shade levels. Across our monitored farms, 18.9% of farm NPP was harvested (i.e., whole cocoa pods) and only 1.1% (i.e., cocoa beans) was removed from the system, suggesting that the scale of HANPP in smallholder cocoa agroforestry systems is relatively small.
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| 2. |
- Morel, Alexandra C., et al.
(författare)
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The Ecological Limits of Poverty Alleviation in an African Forest-Agriculture Landscape
- 2019
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Ingår i: Frontiers in Sustainable Food Systems. - : Frontiers Media SA. - 2571-581X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Cocoa yields in Ghana remain low. This has variously been attributed to low rates of fertilizer application, pollinator limitation, and particularly dry growing conditions. In this paper we use an African forest-agriculture landscape dominated by cocoa (Theobroma cacao) to develop an ecological production function, allowing us to identify key ecological and management limits acting on cocoa yields simultaneously. These included more consistent application of fertilizers inter-annually, distributing rotting biomass throughout the farm and reducing the incidence of capsid attacks. By relaxing these limits, we estimate plausible increases in yields and, by extension, farm incomes. Our analysis reveals that resulting increases in cocoa yields requiring both ecological and intensive management interventions could be significant (113 ± 60%); however, benefits are disproportionately realized by the wealthiest households. We found that wealthier households benefited proportionally more from ecological intensification methods (e.g., leaving more rotting biomass in their farms) and the poorest households benefited proportionally more from capital-intensive intensification methods (e.g., pesticide and fertilizer applications). We treated poverty as multi-dimensional, and show that only certain dimensions of poverty (school attendance, assets, and food security) are significantly related to cocoa incomes, while several other dimensions (access to clean water, sanitation and electricity, and infant mortality) are not. We explore how increased household cocoa incomes could impact different dimensions of poverty. Our findings suggest, that if all households adopted the optimal level of each of these management options, and in so doing had similar poverty profiles to those households already managing optimally, we would see the community-averaged probability: a child of a household misses school decrease from 47 to 31%, a household would be able to acquire assets increase from 40 to 59% and a household would have access to an adequate amount of food increase from 62 to 79%.
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