An assessment of environmental impacts of plant invasive species on Mulanje mountain forest reserve (MMFR) in southern Malawi

Abstract

n environmental impact assessment of woody plant invasive species was conducted on Mulanje Mountain Forest Reserve in Malawi where plant invasive species are regarded as the second largest threat to conservation of biodiversity after direct habitat destruction (EAD, 2006). The main aim was to investigate the ecological and social impact of plant invasive species on Mulanje Mountain Forest Reserve (MMFR) in order to ascertain means of addressing the possible effects on the communities in adjacent to the reserve and on its ecology. Specifically, the study aimed at assessing the spatial distribution and ecological impacts of invasive species on MMFR, evaluating the social impact of invasive species on adjacent communities and identifying appropriate methods for managing invasive species and their impacts on the reserve. It was hypothesized that invasive species have no significant ecological impacts on the biodiversity of Mulanje Mountain Forest Reserve, that invasive species have no significant social impacts on the communities adjacent to the Reserve and that Current methods used in managing impacts of invasive species in Mulanje Mountain Forest Reserve are not effective. In order to meet the objectives, bot h primary and secondary data were used for the study. A semi-structured questionnaire was used to collect primary data from the household respondents to get their views on invasive species impact and their management from a sample of 30 respondents who were systematically selected from the five villages surrounding the reserve. Questionnaires were also used to collect data from the key inform ants. The key informants that were interviewed included the Mulanje district Forest Officer (D.F.O.), Mr. Jeffrey Juwawo, the technical officer for the Mulanje Mountain Conservation Trust (MMCT) , The Chairperson of the Village Forest Management Committee (C FMC) and these were purposively selected based on their familiarity with the reserve. Data on ecological impacts were collected using a baseline transect approach through the Point Centred Quarter Method (PCQM) to measure the spatial distributionof invasive species. This involved the use of three 1–1.2 km long transects (eastern, middle and the western transects) while using the PCQM to assess distribution of woody vegetation along the three transects. An interval of 50– 100 m was estimated between any two consecutive observation points along depending on the variability of vegetation cover along the transects. Species diversity was calculated for each transects using the Shannon-Weiner method, (Harris et al. 1983). Data collected were analysed using Chi square and at 95% confidence level after data had been entered and stored in SPSS computer package version 16.0 and Microsoft Office Excel. Views of respondents on invasive species, knowledge of the invasive species, invasive species effect on beneficial plants and on the supply of other ecological goods and services, species form was analysed using chi square test. Chi square test was used to obtain levels of significance for the non-parametric data. Species use, source of invasive Species, Species abundance was assessed using descriptive statistics such as frequencies and Cross Tabs. Crosstabs were used to summarize categorical data and creation of contingency tables. Following the analysis and discussion of the findings of this study, presence of the invasive species is much more significant on the western side of the reserve as the results shows significant difference on the presence of the invasive species (p=0.003). The identified invasive species include pinus patula and Rubus ellipticus.In vasive species have proved to have both positive and negative impact on the livelihood of the surrounding communities of the Re serve as communities benefit from the invasive species through the provision of the ecological goods and services such as timber, firewood and medicine and only 3 % of the respondents included that they are not useful to them. On the other hand, invasive species have also affected the ecosystem by reducing the population of useful species the results have shown that invasive species increase the frequency of forest fires and this lead to biodiversity loss and threatened endangered species by destroying their habitat and thus leading to their extinction. Ecologically, invasive species have caused considerable loss of biodiversity on the reserve through prevention of regeneration of the native species that are endemic to the reserve. They have also shown to be altering plant and animal habitat as well as disturbing the water flow. The fact that invasive species benefit or please someone, their eradication may impose costs to those in benefit; as a result, there may be some resistance in the control or restriction on the use of the invasive species. Therefore management options should take into consideration of both costs as well as the negative. It was therefore recommended that reforestation programs should be implemented by planting trees with the same values as those of the invasive species to replace then so as not to lose the benefits at the same time maintaining the ecological integrity of the reserve