Analysis of the Dynamics of Forest Landscape Fragmentation in Western Madagascar under the Influence of Migration

Population growth and agricultural expansion, particularly in developing countries, are the main causes of deforestation and forest degradation (Jallat et al., 2021; Ahmed et al., 2023). Forests are among the natural resources whose preservation is a key concern for sustainable development, particularly given the importance of their numerous ecosystem services to both current and future generations (Wainger et al., 2010). Covering a total area of 10 million km² (Senior et al., 2019), tropical forests constitute one of the world's most ecologically important habitat types (Hending et al., 2025). They harbour more than half of the world's forest carbon and more than 80% of terrestrial biodiversity; they play a fundamental role in regulating the climate at both regional and global levels and provide countless services and products to people (Sist, 2025). Unfortunately, tropical forests are among the most threatened habitats in the world (Edwards et al., 2019). Due to factors ranging from large-scale forest conversion to the overexploitation of resources for subsistence purposes, tropical forests have been massively affected by agricultural activities that drive deforestation and forest degradation (Achard et al., 2004; Asner et al., 2009). Currently, most of the remaining tropical forests are fragmented into more than 130 million patches, with an average area of around 29 ha (Taubert et al., 2018). Forest fragmentation manifests itself through typical changes in the spatial structure of the landscape and is characterised by an increase in the number of patches, a reduction in their size, greater complexity in their shape and increased isolation between them (Ma et al., 2023; Peptenatu et al., 2023; Rahman and Islam, 2021). However, the spatial configuration of landscapes, including plot shape and connectivity, plays a crucial role in the provision of ecosystem services (Lamy et al., 2016). This observation highlights the significant impact of forest fragmentation, particularly in areas with high population density, on the continuity and effectiveness of these services (Hisham and Hua, 2026).

Climate-related events are forcing thousands of people to move within their own countries (Veron, 2020). This climate-induced migration directly alters population growth rates and demographic characteristics, both through the migration itself and by interacting with and amplifying other demographic processes (Hauer et al., 2024). As such, the issue of demographic pressures remains a major and pervasive concern in documents examining deforestation, land degradation, the loss and degradation of biodiversity, threats to peace, future stability, and global warming (Agrawal, 2018). In recent years, the forests of sub-Saharan Africa have been under increasing pressure, mainly due to demographic pressure and migration caused by climate change (Nicoletti et al., 2023; Vinke et al., 2022). In these countries, access to land is considered important for improving the incomes and food security of rural households (Holden and Otsuka, 2014; Muraoka et al., 2018). However, migrants often adopt unsustainable agricultural practices (Sunderlin and Pokam, 2002), including itinerant slash-and-burn agriculture. Changes in land use linked to human development are the main drivers of forest fragmentation. With population growth and economic expansion, forests are cleared for agriculture, urbanisation and infrastructure development (Perea, 2024).

The establishment of protected areas is the cornerstone of conservation policies aimed at reducing biodiversity loss and ensuring the long-term conservation of nature, ecosystem services and the associated cultural values (Vimal et al., 2021). However, protected areas in Africa are generally highly vulnerable, due to their proximity to settlements and the impacts of human activities (Triplet, 2009). Furthermore, human migration to resource-rich border regions can be a significant driver of forest change and biodiversity loss (Jones et al., 2018), thereby threatening the integrity of protected areas (Scholte and De Groot, 2010).

As for Madagascar, although it is recognised as one of the world's most biodiverse countries and is classified as a biodiversity hotspot, with a very high rate of endemism, its biodiversity is under severe threat from human activities (Myers et al., 2000; Tovondrazane et al., 2020). As a result, the level of forest fragmentation has been steadily increasing since 1953 (Vieilledent et al., 2018) and, by 2024, forest cover will account for only 20.7% of the island's total land area (Rakotoarisoa et al., 2025).

Although the link between human migration and the degradation of natural resources has been recognised for some time, the role of migration in environmental change continues to attract growing interest in its many facets (Bechard, 2018). In recent years, the link between climate-induced human mobility and environmental health has attracted increasing attention. Deforestation, land loss and forest fragmentation are among the most significant environmental issues threatening forest ecosystems worldwide (Ravonjimalala, 2019). Nowadays, the fragmentation of natural forests, largely linked to human activities, agricultural practices and the expansion of road networks, is a recurring phenomenon faced by tropical countries (Hending et al., 2025; Mahapatra et al., 2025). Consequently, the fragmentation of these tropical forests and protected areas leads to a loss of habitat and biodiversity, as well as an increase in carbon emissions (Hansen et al., 2020).

The Central Menabe region is still home to the largest remnant of dry forest in western Madagascar. These forests harbour a rich biodiversity, including several local and regional endemic species (Zinner et al., 2014), the most famous of which are Hypogeomys antimena, the largest endemic rodent in Madagascar; Microcebus berthae, the world's smallest lemur (Wilmet et al., 2022; Markolf et al., 2019). Central Menabe has a long history of forest conversion to agricultural land, for both plantations and subsistence farming (Scales, 2011). The expansion of agricultural land and plantations, together with forest fires, is currently intensifying forest fragmentation, posing a profound and irreversible threat to forest ecosystems (Caron et al., 2023; Fischer et al., 2021).

Well known for its dense dry forests and mangroves, the Menabe region is renowned for having welcomed and integrated groups of migrants from all over Madagascar, particularly from the south, and is considered a prime destination for internal migration (IOM, 2024). Furthermore, this human mobility affects forest management in several regions of Madagascar (Rabemananjara, 2014), including Menabe Antimena, but there is no evidence of spatial overlap or correlation with deforestation (Rakotonarivo et al., 2026). Within this protected area, migrants from the south settle and cultivate land cleared through slash-and-burn practices, or 'Hatsake', leading to significant deforestation and land grabbing, in defiance of conservation efforts and participatory ecosystem management with local communities (MEDD, 2022). The protected area recorded an annual deforestation rate of 0.85% (2000–2010) rising to 2.35% (2010–2014) (Salvaterra & INDRI, 2017), and is estimated at 4.27% per year (2018–2022); 2.50% (2022–2023) (Andrianambinina et al., 2025) due to the illegal cultivation of maize (Zea mays) and peanuts (Arachis hypogaea) (MEDD, 2022). Consequently, forest cover in Menabe Antimena decreased by 22.1% between 2017 and 2022 (Andrianandrasana et al., 2025).

This reduction in forest area is accompanied by fragmentation, whereby forest plots are divided into several smaller plots (Taubert et al., 2018), and forests fragmented by human activities are at greater risk of further fragmentation or loss than those fragmented by natural causes (Wade et al., 2003). There is good evidence that forest fragmentation has a significant impact in maintaining ecosystem services and is generally recognised as a stressor for ecosystem stability (Fu et al., 2025; Li et al., 2022). In this regard, there is a significant lack of scientific analysis, particularly concerning the causal relationships between landscape spatial configurations and the ecosystem services provided by protected areas.

However, previous studies carried out within the Menabe Antimena protected area have not highlighted the heterogeneity, the degree of temporal and spatial fragmentation, the evolution and their correlation with migration patterns within and around their green belts. Many questions therefore remain unanswered, notably to what extent the migratory influx that occurred between 2017 and 2022 has altered the degree of fragmentation and the spatial configuration of the Menabe Antimena forest landscape. If this migration were to lead to an expansion of subsistence farmland, then the number of forest fragments would increase, as new arrivals clear the denser forest blocks to practise agriculture. Thus, the primary scientific aim of this research is to characterise and quantify the changes occurring in the forest landscape, and to examine the spatial and temporal dynamics of fragmentation in a dry forest in the western ecoregion of Madagascar between 2017 and 2022, whilst assessing its impact on ecosystem resilience. Secondly, to provide a scientific analysis of human migration flows as an independent predictor of vegetation dynamics within the protected area. The results of this study contribute to a better understanding of the relationship between forest fragmentation and agricultural expansion by migrant and indigenous populations, and will serve as a warning and a catalyst for mobilising all stakeholders to develop realistic development policies in the regions from which migrants originate and to devise effective strategies for forest sustainability.