Ecological changes induced by full-sun cocoa farming in Côte d’Ivoire

Abstract

h i g h l i g h t s• Ecological impacts of sun-grown cocoa farming in Côte d'Ivoire were assessed. • Biodiversity and soil properties were measured along a chronosequence. • Plant species richness and diversity markedly decreased from forest to cocoa stands. • Earthworm abundance and species richness increased due the appearance of species adapted to degraded lands. • Full-sun cocoa farming significantly deteriorated soil quality. a b s t r a c tFull-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, * BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/). 576J. E. Tondoh et al. / Global Ecology and Conservation 3 (2015) 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.

Development of a composite soil degradation assessment index for cocoa agroecosystems in southwestern Nigeria

“…For instance, Dawoe et al (2014) reported that, in humid lowland Ghana, soil properties and quality parameters of a Ferric Lixisol improved under cocoa plantations that have been operating for 15-30 years and were better than that of a YCP with a 3-year production age. Similar results were obtained by Tondoh et al (2015), who reported that, in Côte d'Ivoire, there was a steady degradation of soil quality over time in full-sun cocoa stands planted on Ferralsols for 10 years, but the degradation value was less pronounced in 20-year-old plantations.…”

“…Comparing our results with those of Dawoe et al (2014) and Tondoh et al (2015) highlights the effects of poor and unsustainable land management practices on soil degradation in peasant cocoa agroecosystems in West Africa. Traditionally, cocoa plots are cultivated with food crops in the first 3 to 5 years of development until the canopies have formed.…”

“…Soil samples were drawn at the centre of the even-numbered sub-quadrats, resulting in a total of five soil samples per plot. Measurements were deliberately restricted to a depth of 0 to 20 cm for the following reasons: (i) most significant changes in soil characteristics in any vegetation (especially in a tropical environment) are confined to the topmost layer of the soil profile (Aweto, 1981;Aweto and Iyanda, 2003;Tondoh et al, 2015); (ii) these depths cover the main distribution of roots and soil nutrient stocks of cocoa plantations (Hartemink, 2005) and is therefore usually used in soil surveys for fertilizer recommendations in West African cocoa-based agroecosystems (Snoeck et al, 2010); (iii) several studies (e.g. Isaac et al, 2007) demonstrated that cacao trees tend to have shallow root activity within the topsoil (0-20 cm); (iv) biological processes, such as earthworm activities, are restricted to 0-10 cm layer of tropical soils; (v) measurements were restricted to facilitate future replication of the methodology as routine soil samples are usually taken from the topsoil layer (plough layer); and (vi) the soil degradation index developed in this study is expected to be used by farmers and extension officers for rehabilitating degraded cocoa plantations in the study area and similar environments, and by confining the samples to the topsoil, the likelihood of adoption by the end users is greater.…”

“…Cocoa (Theobroma cacao L.) agroecosystems are a major agricultural land use type in the tropical rainforest belt of West Africa (Tondoh et al, 2015), covering an estimated total area of about 6 million ha in Côte d'Ivoire, Ghana, Nigeria, and Cameroon (Sonwa et al, 2014). Unfortunately, cocoa landscapes are often associated with a range of ecological changes including deforestation, biodiversity loss, destruction of soil flora and fauna from pesticide usage, and accelerated soil degradation (Critchley and Bruijnzeel, 1996;Salami, 1998Salami, , 2001Rice and Greenberg, 2000;Asare, 2005;Ntiamoah and Afrane, 2008;Mbile et al, 2009;Adeoye and Ayeni, 2011;Jagoret et al, 2012;Akinyemi, 2013;Schoneveld, 2014;Sonwa et al, 2014;Tondoh et al, 2015).…”

“…Unfortunately, cocoa landscapes are often associated with a range of ecological changes including deforestation, biodiversity loss, destruction of soil flora and fauna from pesticide usage, and accelerated soil degradation (Critchley and Bruijnzeel, 1996;Salami, 1998Salami, , 2001Rice and Greenberg, 2000;Asare, 2005;Ntiamoah and Afrane, 2008;Mbile et al, 2009;Adeoye and Ayeni, 2011;Jagoret et al, 2012;Akinyemi, 2013;Schoneveld, 2014;Sonwa et al, 2014;Tondoh et al, 2015). Until present, soil degradation assessments on a plot scale in regions undergoing farmland conversion to cocoa agroecosystems have been limited.…”