Original research article
Ecological changes induced by full-sun cocoa farming in Côte d’Ivoire
- Under a Creative Commons license
Highlights
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- Ecological impacts of sun-grown cocoa farming in Côte d’Ivoire were assessed.
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- Biodiversity and soil properties were measured along a chronosequence.
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- Plant species richness and diversity markedly decreased from forest to cocoa stands.
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- Earthworm abundance and species richness increased due the appearance of species adapted to degraded lands.
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- Full-sun cocoa farming significantly deteriorated soil quality.
Abstract
Full-sun cocoa farming is currently the most widespread cocoa cultivation system in humid and sub-humid Côte d’Ivoire. Higher short-term yields from increasing surfaces under cultivation in this farming system have contributed to the country being ranked as top cocoa producer in the world. However the negative consequences including biodiversity loss, soil fertility depletion and soil quality degradation associated with this system, have incredibly received so less attention that the type and magnitude of such agro-ecological consequences within the current context of climate change are worth investigating. The present study was undertaken in the former cocoa belt of Central-Western Côte d’Ivoire, precisely in the Oumé Department. The main objective was to assess the impact of forest conversion to full-sun cocoa plantations on above and below-ground biodiversity along with soil quality by measuring chemical, physical and biological parameters along a chronosequence of different ages (5, 10 and 20 years). The results are summarized as follows: (i) the conversion of semi-deciduous forests to cocoa plantations resulted in plant diversity and species richness loss due to the disappearance of a huge number of native species while earthworm abundance and species richness increased due to the appearance of species adapted to degraded lands, (ii) soil quality was severely impaired by cocoa farming with the worse scenario being found under the 10-year-old cocoa plantations, where SOC, total N, CEC contributed mostly to soil quality degradation. The contribution of these findings to devise options for sustainable tree-based cocoa farming is discussed.
Keywords
- Biodiversity;
- Cocoa plantations;
- Côte d’Ivoire;
- Soil quality
1. Introduction
Cocoa farming is the most widespread land use system in the Guinean rain forest (GRF) of West Africa (Gockowski and Sonwa, 2011), an area stretching from Guinea to Cameroon that has been identified 20 years ago as a global biodiversity hotspot (Myers et al., 2000). Cocoa production in Côte d’Ivoire expanded rapidly in the 1980’s, becoming for the last 20 years, the largest cocoa producer in output and number of producers in the world currently holding more than 40% of the world market followed by Ghana, Nigeria and Cameroon (Gockowski and Sonwa, 2011 and Hartemink, 2005). In humid and sub-humid areas of the country, these plantations are estimated to cover 1,924,056 ha with a global annual production amounting to 1,337,161 Mg (data from 2000–2006, Anonymous, 2006). The increase in area under cocoa plantations has been at the expense of forest cover as it is estimated that over 2.3 millions ha of deforestation and forest degradation in the GRF is associated with this most widespread land use system (Gockowski and Sonwa, 2011). Moreover, the significant reduction of forest cover ranging from 12 to 2.2 million ha between 1955 and 1993 in Côte d’Ivoire has been found to coincide with the strong increases in cocoa and coffee production (Leonard and Oswald, 1996 and Brou et al., 1998), which corresponded to a deforestation rate of 7.6% per year (Balac, 1999).
In West Africa, cocoa farms are mostly established following a similar model referred to as short-term “boom-and-bust cycles” (Tscharntke et al., 2011): primary or secondary forests are selectively cleared, burned and cocoa is planted along with understory food crops (Isaac et al., 2005). After 20 and 25 years of cropping, the production decreases significantly and plantations are abandoned (Ruf and Zadi, 1988), and the centre of cocoa production typically moves to other areas. In Côte d’Ivoire, this resulted in the emergence of three major cocoa production zones over time (Balac, 1999): (i) the east and central-east (1955–1965), the central-west (1965–1975), and the southwest region (since 1975). In addition, the degree of shade in cocoa stands ranges from 24.5 to 48.1% showing the predominance of full-sun cocoa farming systems in the country with 28.2 to 37.5% of shade in the centre-west region hosting the present study (Gockowski and Sonwa, 2011).
Thus, the long-term conversion of forest to full-sun cocoa plantations might result in agro-ecological drawbacks such as forest degradation, biodiversity loss, soil quality disruption associated with low yield and food insecurity; and greenhouse gas emission as pointed out by several authors (Zapfack et al., 2002,Asase et al., 2009, Lal, 2009, Gockowski and Sonwa, 2011 and Tscharntke et al., 2011). However the impacts of such an unsustainable land use change practice, which is widespread in the country with devastating environmental impacts in the long run, have rarely been assessed to provide necessary baseline figures relevant for future rehabilitation actions.
Although information about agro-ecological consequences in current and old main cocoa production zones in Côte d’Ivoire is limited, signs of land degradation such as low cocoa production, drop in economic activities, soil fertility depletion, food insecurity and decrease in cocoa-cultivated surfaces in former “cocoa belts” are clearly visible. Assessing changes in agro-ecological environments along a chronosequence of sun-grown cocoa plantations in one of the former cocoa belt, seems to be the most relevant approach to find out the magnitude of impact over time, as reported recently in Ghana (Dawoe et al., 2014). It also the first step towards identification of efficient options to reverse land degradation associated with full-sun cocoa farming.
The current study was designed to fill in this gap by gathering empirical data on biodiversity loss and soil quality degradation as a consequence of sun-grown cocoa farming in Côte d’Ivoire. The objective was to assess the impact of these cocoa plantations on biodiversity and soil quality along a chronosequence of cocoa plantations from those recently established after conversion to old growth stands of 20 years. This study is a first attempt to assess soil health deterioration due to sun-grown cocoa cropping in Côte d’Ivoire. We tested the general hypothesis that full-sun cocoa farming in Côte d’Ivoire results in biodiversity loss and soil quality deterioration leading to short-term abandonment of plantations. Finally, in light of results generated, options for sustainable cocoa farming will be outlined based on previous works.
