Asset-Based Adaptation Project Promotes Tree and Shrub Diversity and Above-Ground Carbon Stocks in Smallholder Agroforestry Systems in Western Kenya

Abstract

Agroforestry has potential to address the adverse effects of climate change through carbon sequestration, increasing biodiversity and improving adaptive capacity and resilience among smallholder farmers. However, this potential is context specific and insufficiently quantified in smallholder faming systems, partly because of inherent variability of smallholder farms. Our study aimed to determine the tree/shrub diversity and carbon stocks in different agroforestry systems within smallholder farms in two 100 km2 sites, the so-called lower and middle Nyando sites, in western Kenya. In both, context-specific agroforestry adoption had been promoted among households of four community associations through an asset-based community development (ABCD) approach. Their farms were assessed and compared with those of relevant comparison samples. Trees and shrubs were inventoried on a total of 106 farms, and their formations classified in five major agroforestry practices: hedgerows, multipurpose trees on farm (MPT), riparian buffers, woodlots, and boundary planting. To assess above-ground biomass (AGB) of individual trees/shrubs, diameter at breast height measurements were taken. Strong regional differences were considered in data analysis and presentation. Altogether, 3,353 and 6,346 trees/shrubs were inventoried in the lower and middle Nyando sites, respectively. AGB was significantly higher in middle than in lower Nyando. Woodlots had the highest amount of AGB carbon stock, while MPT had the highest diversity of tree/shrub species in all the groups. Conversely, boundary planting had the highest number of trees/shrubs inventoried and hence was the most common agroforestry practice across all the samples in both regions. Dominant AGB contributor species were Grevillea robusta (37.8%) in middle, and Eurphobia tirucalli (16.5%) in lower Nyando. This study provides empirical evidence that asset-based and community-driven selection and implementation of both tree/shrub species and agroforestry practices can contribute positively to species and practice diversity, which are associated with AGB carbon stock levels and wider agro-ecosystem diversity. This study hence provides benchmark information that is relevant for SDG goal 15 on “life on land,” and various specific targets, and can inform sustainable establishment of carbon sink facilities by supporting smallholders to uptake contextually suitable and economically sensible agroforestry practices in an overall effort to foster and support sustainable development.

Exploring the Ecological Effects of Rural Land Use Changes: A Bibliometric Overview

“…Agroforestry, integrating trees and shrubs into agricultural landscapes, fosters a beneficial synergy between agriculture and forestry, enriching biodiversity, soil structure, and carbon sequestration [106]. In Kenya, agroforestry initiatives by smallholder farmers, involving nitrogen-fixing trees, have notably improved soil fertility, agricultural productivity, and wildlife habitats, illustrating the environmental gains from effective green space management [107]. Furthermore, the restoration and judicious management of wetlands are crucial for enhancing water quality, supporting wildlife habitats, and providing natural flood management [108].…”

Tree growth as an effect indicator of silvopastoral systems in the low hilly area of western Henan province, China

“…Pure forests and silvopastoral systems (i.e., forest and grass composite systems, see Nair, 1985) have been widely used to restore these ecologically fragile areas (Grewal et al, 1994;Chebli et al, 2021;Olaya-Montes et al, 2021). Compared to pure forests, silvopastoral systems can often increase soil fertility (Amatya et al, 2002;He et al, 2013;Fuchs et al, 2022) and increase herbaceous plant/animal biodiversity (Wyss, 1996;Kong et al, 2001;Santos et al, 2019). However, most studies are confined to the effect of silvopastoral systems on soil quality, and the responses of tree growth to silvopastoral systems are not well examined in low hilly areas.…”

Trade-Offs in Tree Species Selection and Carbon Offset on Farms Adjacent to Kakamega-Nandi Forest Ecosystem in Kenya

“…The amount of carbon stored in trees on farmlands is context specific and varies depending on factors such as agroforestry practices, type of species planted, age of agroforestry system, management influence, and environmental conditions (Luedeling, Sileshi and Dietz, 2011;Kuyah et al, 2014). In western Kenya, two studies estimated carbon in agroforestry systems to be 17 Mg ha -1 in above ground biomass (Kuyah et al, 2012b) and 5 Mgha -1 in below ground biomass (Kuyah et al, 2012a;Mbow et al, 2014), totaling 22 Mg ha -1 of carbon in living biomass (Fuchs et al, 2022). This research was part of the Sustainable Land Management (SLM) project in western Kenya (Kakamega, Nandi and Vihiga counties) which involved adoption of practices by farmers that contribute to conservation of soil and increased amount of organic carbon in the soil which in turn results to higher yields..…”