Assessing and mapping ecosystem services of trees outside forest

Abstract

Trees Outside Forest (TOF) are naturally grown or planted trees in croplands which are retained by local beneficiaries except commercial plantation trees such as cacao and teak plantations. TOF are scarce in terms of total coverage and presence compared to trees within forests. TOF play a vital role in the supply of various ecosystem services such as provisioning, regulating and cultural services. However, the role of TOF in the supply of ecosystem service is missing from forest assessments and policies. In rural areas and croplands, there is no sufficient information why TOF are retained by local beneficiaries. The identification of why the beneficiaries retain these trees and what ecosystem services are provided by these trees contribute to a better understanding of TOF distribution and changes. A better understanding of who profits from what trees can help to arrange protection and management of TOF. Information about the location and important ecosystem services and their values supplied by TOF to local and national beneficiaries can lead to better planning for decisions to support species and ecosystem service delivery, identify and inform management strategies for better benefits, identify areas that require special management and provide information to increase awareness to local beneficiaries and government support for evidence-based policy and management decisions. The overall objective of this MSc study was to map TOF in croplands and assess their contribution to the supply of ecosystem services for local and national beneficiaries using participatory research, Google Earth and ArcMap in Ghana as case study area. Participatory research with local beneficiaries was applied to conduct a species inventory of TOF and to identify and value the local ecosystem services provided by TOF species. The national ecosystem service of climate change regulation (the amount of carbon stock) in each TOF were mapped based on field measurements and the TOF species were valued based on the average amount of carbon stock using carbon market price. A satellite image available from Google Earth was used to map croplands, and ArcMap was used to calculate the local and national ecosystem service hotspot areas based on the values assigned to each TOF individuals. The research identified a total of 786 TOF individuals and 50 TOF species in 147 ha of croplands in the study area. Ficus exasperate, Morinda lucida, Ceiba pentandra, Spathodea campanulata, Mangifera indica, Sterculia tragacantha, Funtumia elastic, Ficus carpensis, Vernonia amygdalina and Trilipisium madagascariense are the top ten most dominant species in terms of species occurrence. Fifteen different local ecosystem services supplied by TOF species were identified and valued of which shade (supplied by 44 TOF species), charcoal (by 2 species), pollination of cacao plants (1 species), timber (32 species), medicine (24 species), soil fertility (15 species) and soil conservation (14 species) were valued the most. The total carbon stored by all 786 TOF in 147 ha of the study area is 759 tons of carbon. The most important TOF species and hotspot locations that require special planning, conservation, and management focus was identified, mapped and assessed. There was a poor correlation between the values of the key species for local and national beneficiaries which might lead to conflict of interest and illegal tree felling. Based on the ecosystem service values for local and national beneficiaries 30% of the top ten TOF species were the same for both beneficiaries. The pattern of the hotspot analysis showed that most of the locations of the key TOF species for local beneficiaries are different from national beneficiaries. The result of this MSc research can contribute to managers and national policy makers of TOF to identify the interest of local and national beneficiaries to resolve conflicts of interest and illegal tree cutting and focus their planning and management on the most important TOF species which are highly valued and multifunctional.