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A comparative assessment of biodiversity changes in Echuya Central Forest Reserve following anthropogenic activities between 2015 and 2021

Publication overview

Biodiversity is one of the fundamental properties of nature and source of immense potential for economic use and yet the ecological functions performed by the biological diversity are still less understood. Tropical forests are arguably the most biologically diverse places on planet with many endemic and rare species within. Unfortunately an estimated 154 million ha of these tropical forest are cleared each year by human activities for mainly cattle ranching and agriculture. Deforestation of the tropical forests comes in many forms that include wild fires, clear-cutting, unsustainable logging for timber and degradation due to climate change all caused by humans.

The Echuya Central Forest Reserve (ECFR) is not as very rich in biodiversity like the other forests of Bwindi and Mgahinga but is considered of high conservation importance because of its endemic, rare and globally threatened flora, and fauna. Some of the species found in ECFR include the African Golden Cat (Caracal aurata), Rodents (Lophuromys woosnami, Delanymys brooksi, Ruwenzorisorex suncoides), and Birds - Grauer’s Swamp Warbler (Bradypterus graueri) and the Abyssinian Ground-Thrush (Geokichla piaggiae). Unfortunately, these unique and rare species (including overall biodiversity) in ECFR is under serious threat from anthropogenic activities. In June 2018, the biodiversity threats to ECFR were further exacerbated, when the National Forest Authority (NFA) carried out massive bamboo forest understory clearance/weeding by cutting and removing all tree saplings, vines, shrubs, and lianas under the bamboo forest. This study therefore assessed the impact of the different anthropogenic activities (illegal activities and the forest understory clearance) on the biodiversity of ECFR.

Three taxa; vegetation (trees, shrubs, lianas, vines, and herbs), terrestrial vertebrates (small mammals) and birds were used as surrogate indicator species for the assessment of the status of total biodiversity of ECFR. Furthermore, the study used the biodiversity assessment done in 2015 as baseline to compare the changes in biodiversity currently (2021). Human activities in ECFR of 2021 were also recorded and compared with those previously done in 2015 (baseline). After analyzing the field data collected in 2015 and 2021 using R open-source statistical software version 3.2.2, the study came out with the following results.

A total of 27 tree species were recorded in ECFR for 2015 and 2021 study period. Of these, Macaranga capensis, Psychotria mahonnii, Xymalos monospora, Neoboutonia macrocalyx, Maesa lanceolata and Nuxia congesta were the most dominant tree species in descending order. A comparison of the most dominant tree species between 2015 and 2021 shows that Macaranga capensis constituted over 64% of the tree species in ECFR in 2015 but reduced to 34% in 2021 giving way to other tree species. There was no significant difference in the abundance of tree stems (expressed per unit hectare) recorded in 2015 and 2021. However, tree species evenness (abundance) and richness (diversity) were higher in the year 2021 (twice) than 2015.

A total of 60 shrubs and lianas were recorded in ECFR for 2015 and 2021 study period. Of these, the most dominant shrub and liana species in descending order were Mimulopsis Solmsii, Triumfetta cordifolia, Phillipia denguelinsis, Dracaena laxissima, Urera hypselodendron, Piper capense, and Rhamnus prinoides. The abundance of the shrubs and lianas (expressed per unit hectare) were not significantly differently between 2015 and 2021. In terms of species evenness and richness (diversity), the year 2015 recorded higher values than 2021, with the implication that since 2015, ECFR could have lost some shrub and liana species perhaps from the forest understory clearing carried out in 2018.

A total of 92 vines and herbs were recorded in ECFR for 2015 and 2021 study period. Of these, the most dominant vine and herb species in descending order Alchemilla johnstonii, Drognetia iners, Asplenium spp, Panicum adenophorum, Acalypha pinata and Panicium spp. The relative abundance of the vines and herbs (expressed per unit hectare) were not significantly different in 2015 and 2021. Species evenness and richness of the vines and herbs was higher in 2015 than in 2021, with the implication that since 2015, ECFR could have lost some vines and herb species perhaps from the forest understory clearing carried out in 2018.

A total of 15 rodent species were recorded in ECFR for 2015 and 2021 study period. Of these, the most dominant rodent species in descending order were Myomys Funatus, Mastomys natalensis, Laphuromys spp., Dasmys incomptus and Lophuromys flavopunctatus. The relative abundance of the rodents (expressed per unit hectare) was not significantly different between 2015 and 2021. Furthermore, the rodents’ species evenness and richness in 2015 and 2021 were similar.

A total of 103 bird species were recorded in ECFR with 72 species in 2015 and 82 species in 2021 study periods. The avifauna of Echuya showed some changes between 2015 and 2021 related to increased level human disturbances in the CFR. There is still a high number of forest birds but a large proportion of the bird community are the forest generalists or forest edge species (F-species) that are of low conservation significance since they are widely distributed. There was also an increase in species density. However, the increase was due to the invasion of non-forest species exploiting new habitats. Further disturbance is likely to lead to loss of more forest species like the forage gleaners that depend on dead trees that are harvested for fuelwood and the ground feeders that depend on bamboo litter which will dry with the removal of more bamboo poles, climbers, and forest understory. The forage gleaners and ground feeders have a highly specialized diet or foraging behavior and are physiologically intolerant of microclimatic changes of a disturbed forest. The increase in the species density of mixed feeders and f-species in some parts of the forest is an indicator of loss of quality of the forest. This study considers only short-term results. However, the responses of any species to disturbance are potentially varied and difficult to predict. There is a need to generate more information on the long-term effects of disturbance on forest bird species that will help management in designing mitigation strategies to reduce the deleterious impacts of human activities on biodiversity.

The forest area that was cleared of forest understory (climbers and other forest understory plants) by NFA in 2018 was calculated to be about 3.6Km2 and is 11% of the entire ECFR area coverage. The most prevalent human activities recorded in ECFR for both 2015 and 2021 in descending order were fresh human trails, pole cutting, livestock grazing, firewood collection and bamboo stem harvesting. The number of human activity signs recorded in ECFR increased from 61 in 2015 to 227 in 2021 and was statistically significant. The human activities in ECFR have been increasing with increased demand of forest resources from the surrounding communities.

The anthropogenic activities within the ECFR have more than tripled since 2015 and these are most likely going to increase in the near future. It would therefore be plausible to conclude that the increased anthropogenic activities in ECFR together with the clearing and cutting of the bamboo forest understory in 2018 have exacerbated the loss in some biodiversity for the ECFR and this is more expressed by the shrubs, lianas, vines, and herbs. Furthermore, because of anthropogenic habitat manipulations in ECFR, some opportunistic tree species seem to have taken the advantage of less competition by increasing in abundance (individuals). Several recommendations have been suggested by this study that include enhanced law enforcement, regulation, and strict enforcements of forest resource harvest quotas for ECFR and proactively increased agroforestry activities in the local communities around ECFR.

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