Conducted jointly with Cirad, this research explores the impact of anthropization on biodiversity in the Togodo Protected Area.
The Essentials: Conducted jointly with Cirad, this research explores the impact of anthropization on biodiversity in the Togodo Protected Area.
Amah Akodéwou, researcher at UPR Forêts et Sociétés (Centre de Coopération Internationale en Recherche Agronomique pour le Développement).
Thesis defended in 2019.
This research is the product of an international joint supervision between several partner institutions.
Context and Research Problem
Between 1974 and 2016, semi-natural vegetation in the Togodo Protected Area, located in southeastern Togo, declined from 67% to 22%. This reduction is the result of land-use changes, driven mainly by agriculture and urbanization. Human activities affect not only the integrity of ecosystems but also biodiversity. The proliferation of invasive plants, which account for 14.70% of the 483 species recorded in the study area, is a significant indicator of this. These plants alter ecosystem structure, leading to losses in agricultural yield and creating a vicious cycle in which intensified agriculture favors their spread. Fallow lands, often neglected, become refuges for these unwanted species, posing challenges for sustainable resource management.
Methodology
Amah Akodéwou's thesis adopts a systemic approach, integrating modern tools such as Geographic Information Systems (GIS) and remote sensing (Landsat and Sentinel 2) to map landscape changes from 1974 to 2016. Four key periods were analyzed: 1974, 1986, 2003, and 2016. Floristic inventories were carried out on 50-meter-square plots, selected based on different land uses and land-use change trajectories. Botanical surveys recorded the abundance and dominance of all plant species present. Frequency analysis was used to study floristic diversity, vegetation structure, ecological profiles, and differential invasive species. In addition, ethnobotanical surveys coupled with direct observations were conducted to document management practices and local populations' uses of invasive plants.
Key Findings
The results of this study reveal a notable increase in cropland area, rising from 33% to 77% between 1974 and 2016. Despite this intensification of agricultural activities and human disturbance, the total floristic diversity of the region is relatively high, with 483 species recorded. The arrival of new species, favored by human actions, even led to an increase in floristic diversity.
Among the recorded species, 71 are classified as invasive or potentially invasive, representing 14.70% of the total. Of the 178 dominant species, 30 are invasive, equivalent to 16.85%. The results indicate that the effects of human activities, such as land-cover types and land-use change trajectories, are more determinant for the presence of invasive species than physical environmental factors such as soil type and geology. Fallow lands are particularly dominated by invasive plants, with Pennisetum maximum, Chromolaena odorata, and Sida costata as the most dominant species.
The study also shows that several invasive plants are used by local populations to feed poultry and cattle, and even for human consumption. These plants provide services such as bioindication, soil fertilization, and pest control.
Discussion and Outlook
The results of this research highlight the urgent need to rethink natural resource management in the Togodo Protected Area and its surrounding areas. The duality of invasive plants, perceived as both a threat and a useful resource, calls for an integrated approach to conservation and agriculture. Scientific validation of agroecological practices could offer a sustainable alternative to chemical inputs, which are often costly and harmful to human health and soil quality.
Data collected through GIS and remote sensing make it possible to identify at-risk areas and develop targeted conservation strategies. Decision-makers should integrate this local knowledge and research findings into land management policy. The situation in Togodo is representative of the challenges West Africa must address regarding biodiversity in the face of anthropization. The decisions made today will have significant repercussions for future generations, and preserving biodiversity must become a priority on political and economic agendas.
Key Data
- 67% to 22%: Decline in semi-natural vegetation between 1974 and 2016.
- 14.70%: Proportion of invasive species among recorded species.
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Sources and Access
Amah Akodéwou. Trajectoires paysagères et biodiversité : effets de l’anthropisation sur les plantes envahissantes à l’échelle de l’Aire Protégée Togodo et sa périphérie dans le sud-est du Togo. Sciences de l'environnement. Institut Agronomique Vétérinaire et Forestier de France (IAVFF), AgroParisTech, 2019. Français. ⟨NNT : ⟩. ⟨tel-02288187⟩