14 research outputs found
Biodiversity, carbon stocks and sequestration potential in aboveground biomass in smallholder farming systems of western Kenya
While Carbon (C) sequestration on farmlands may contribute to mitigate CO2 concentrations in the
atmosphere, greater agro-biodiversity may ensure longer term stability of C storage in fluctuating
environments. This study was conducted in the highlands of western Kenya, a region with high potential
for agroforestry, with the objectives of assessing current biodiversity and aboveground C stocks in
perennial vegetation growing on farmland, and estimating C sequestration potential in aboveground C
pools. Allometric models were developed to estimate aboveground biomass of trees and hedgerows, and
an inventory of perennial vegetation was conducted in 35 farms in Vihiga and Siaya districts. Values of the
Shannon index (H), used to evaluate biodiversity, ranged from 0.01 in woodlots through 0.4–0.6 in food
crop plots, to 1.3–1.6 in homegardens. Eucalyptus saligna was the most frequent tree species found as
individual trees (20%), in windrows (47%), and in woodlots (99%) in Vihiga and the most frequent in
woodlots (96%) in Siaya. Trees represented the most important C pool in aboveground biomass of
perennial plants growing on-farm, contributing to 81 and 55% of total aboveground farm C in Vihiga and
Siaya, respectively, followed by hedgerows (13 and 39%, respectively) and permanent crop stands (5 and
6%, respectively). Most of the tree C was located in woodlots in Vihiga (61%) and in individual trees
growing in or around food crop plots in Siaya (57%). The homegardens represented the second C pool in
importance, with 25 and 33% of C stocks in Vihiga and Siaya, respectively. Considering the mean total
aboveground C stocks observed, and taking the average farmsizes of Vihiga (0.6 ha) and Siaya (1.4 ha), an
average farm would store 6.5 0.1 Mg C farm 1 in Vihiga and 12.4 0.1 Mg C farm 1 in Siaya. At both sites,
the C sequestration potential in perennial aboveground biomass was estimated at ca. 16 Mg C ha 1. With the
current market price for carbon, the implementation of Clean Development Mechanism Afforestation/
Reforestation (CDM A/R) projects seems unfeasible, due to the large number of small farms (between 140 and
300) necessary to achieve a critical land area able to compensate the concomitant minimum transaction costs.
Higher financial compensation for C sequestration projects that encourage biodiversity would allow clearer
win–win scenarios for smallholder farmers. Thus, a better valuation of ecosystem services should encourage C
sequestration together with on-farm biodiversity when promoting CDM A/R projects
Estimates of carbon stocks in sandy soils cultivated under local management practices in Senegal’s groundnut basin
Multi-criteria spatialization of soil organic carbon sequestration potential from agricultural intensification in Senegal
Biomass transfers and nutrient budgets of the agro-pastoral systems in a village territory in south-western Burkina Faso
Application of geostatistical methods for the spatial distribution of soils in the irrigated plain of Doukkala, Morocco
Dynamics of Ecosystem Services during Forest Transitions in Costa Rica
International audienceThe forest transition framework describes the temporal changes of forest areas with economic development. A first phase of forest contraction is followed by a second phase of expansion once a turning point is reached. This framework does not differentiate forest types or ecosystem services, and describes forests regardless of their contribution to human well-being. For several decades, deforestation in many tropical regions has degraded ecosystem services, such as watershed regulation, while increasing provisioning services from agriculture, for example, food. Forest transitions and expansion have been observed in some countries, but their consequences for ecosystem services are often unclear. We analyzed the implications of forest cover change on ecosystem services in Costa Rica, where a forest transition has been suggested. A review of literature and secondary data on forest and ecosystem services in Costa Rica indicated that forest transition might have led to an ecosystem services transition. We modeled and mapped the changes of selected ecosystem services in the upper part of the ReventazĂłn watershed and analyzed how supply changed over time in order to identify possible transitions in ecosystem services. The modeled changes of ecosystem services is similar to the second phase of a forest transition but no turning point was identified, probably because of the limited temporal scope of the analysis. Trends of provisioning and regulating services and their tradeoffs were opposite in different spatial subunits of our study area, which highlights the importance of scale in the analysis of ecosystem services and forest transitions. The ecosystem services transition framework proposed in this study is useful for analyzing the temporal changes of ecosystem services and linking socio-economic drivers to ecosystem services demand at different scales