Living with landslides: Land use on unstable hillslopes in a rural tropical mountainous environment in DR Congo

Landslides are a common natural hazard on numerous hillslopes across the world. The negative impacts of landslides are well documented, including loss of life, significant property damage, soil degradation and sedimentation of rivers (Garwood et al., 1979; Petley, 2012; Dowling and Santi, 2014; Clark et al., 2016; Haque et al., 2016; Froude and Petley, 2018; Li et al., 2022). Yet, in densely-populated rural mountainous regions where land management regulations are limited and intensive farming is not the norm, local communities often have no choice but to live on steep terrains naturally impacted by landslides (Depicker et al., 2021). Besides, landslides may also be a source of opportunity for people. This is because landslides can modify land characteristics such as topography, soil moisture or soil type in such a way as to provide for new opportunities. For instance, on Mount Elgon on the Uganda-Kenya border, Van Eynde et al. (2017) showed that landslides older than 60 years have a higher organic matter content than on adjacent land, a key component of soil fertility. Landslides may also lead to the outcrop of exploitable materials or minerals, as observed in the Kivu region of DR Congo (Maki Mateso et al., 2023). Changes in land characteristics within landslides can also enhance biodiversity (Alexandrowicz and Margielewski, 2010; Temme, 2021) or induce alternative land uses (Walker and Shiels, 2013). For instance, the flatness of the source area of large landslides can provide favorable topography for infrastructure development or even for establishing entire villages in mountainous regions (Hewitt, 2010). For an area in the Outer Carpathians in Poland, Kroh (2017) reported that the proportion of forest was 11 % higher, and the proportion of cropland 3 % lower, in landslides compared to areas outside landslides. However, apart from the latter study, the way landslides are being exploited and the factors influencing this exploitation have not been studied in detail to date (e.g., Walker and Shiels, 2013; Hu et al., 2018; Nakileza and Tushabe, 2018).

Tropical mountainous regions are particularly susceptible to landslides (Stanley and Kirschbaum, 2017; Broeckx et al., 2018; Dewitte et al., 2022). In these regions, studies have mainly focused on the role of natural factors (e.g., rainfall, soil weathering) and of (changes in) land use patterns in landslide occurrence (e.g., Guns and Vanacker, 2012; Depicker et al., 2020). Additional studies have also addressed the direct impacts of landslides as well as the perception of causes and risks in order to improve awareness and management of landsliding and the resilience of population to this type of disaster (Misanya and Øyhus, 2015; Alcántara-Ayala and Moreno, 2016; Mertens et al., 2016; Masaba et al., 2017; Mertens et al., 2018; Pham et al., 2019). However, because conditions in tropical mountainous areas are often more favorable than in tropical lowlands in terms of climate, soil types or sanitary pressure, these regions are commonly densely inhabited (Nyssen et al., 2009; Eze et al., 2021). As a result of the high land pressure, every piece of land counts, even those that are located on landslides (Mertens and Vranken, 2018).

The present research therefore aims to go beyond a classical study on the negative impacts of natural hazard risk such as landslides. Instead, this work aims at understanding the rationale underlying land use in landslide affected landscapes with a specific focus on rural environments. To do that, we focus on the populated tropical environment of the Rift flank west of Lake Kivu in DR Congo, a densely-populated mountainous region subjected to numerous landslide processes of varying ages and sizes (e.g. Maki Mateso et al., 2023). Specifically, the objectives are to: (1) assess knowledge of landslides and perception of landsliding risk by farmers as a function of landslide characteristics, (2) assess to what extent landslide characteristics condition the perception of the land value and the degree of satisfaction at exploiting land located in landslides, (3) determine the types and extent of land use in landslide-affected landscapes.