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Modeling the multi‐functionality of African savanna landscapes under global change

Various recent publications have indicated that accelerated global change and its negative impacts on terrestrial ecosystems in Southern Africa urgently demand quantitative assessment and modelling of a range of ecosystem services (Chaplin-Kramer et al., 2019; Conway et al., 2015; IPCC, 2019) on which rural communities depend. Information is needed on how these Ecosystem Services (ES) can be enhanced through sustainable land management interventions and enabling policies (Rötter et al., 2005; Sikora, Terry, Vlek, & Chitjja, 2020). Yet, it has also been claimed that, to date, the required system analyses, data and tools to quantify important interactions between biophysical and socio-economic components, their resilience and ability to contribute to livelihood needs do not exist (Midgley & Bond, 2015; Sikora et al., 2020). We disagree, but acknowledge that building an appropriate integrative modelling framework for assessing the multi-functionality of savanna landscapes is challenging. Yet, in this Letter-to-the-Editor, we show that a number of suitable modelling components and required data already exist and can be mobilized and integrated with emerging data and tools to provide answers to problem-driven questions posed by stakeholders on land management and policy issues. High population growth, persistent low agricultural productivity and poverty, severe land degradation, and high climate variability, among other things, have already led to a decline of essential ES in many regions of Africa. The situation is particularly critical in the savanna regions of Southern Africa, which are considered hotspots of global change impacts that lead to a deterioration of ES (Conway et al., 2015; IPCC, 2019; Sikora et al., 2020). Accelerated climate change is putting additional pressure on their multi-functionality (Conway et al., 2015; Midgley & Bond, 2015). ES such as provision of food, feed, fuel, carbon sequestration, nutrient cycling, habitat quality, pollination, and natural pest control are under threat (IPCC, 2019; Sikora et al., 2020). Southern Africa has also been identified as a hotspot for biodiversity, whereby agricultural expansion is seen as a key driving force for the declining species diversity (IPBES, 2018). The projected doubling of the African human population by 2050 and the climate change-induced increased frequency of extreme droughts underline the urgent need for science-informed assessments as a prerequisite for identifying sustainable land management options (IPCC, 2019; Sikora et al., 2020). About 70% of the population of southern Africa relies on agriculture. Most of these people are smallholders of which about 94% depend on rainfed agriculture. Around 16% of the rural population has been characterized as ‘food insecure’ during the last 5 years (Sikora et al., 2020). Climate variability, climate change, changes in land-use, technological advances, institutional and policy constraints as well as the current status of ES determine whether and to what extent the most relevant sustainable development goals (SDGs) can be achieved, specifically: No poverty (1), Zero hunger (2), Clean water (6), Climate action (13), and Life on land (15). Southern African savanna landscapes are composed of arable land, rangelands and orchards/homegardens and host unique nature parks (IPBES, 2018; Midgley & Bond, 2015; Sikora et al., 2020), which are, however, excluded from our analysis. Rural livelihoods, especially those of smallholders, who commonly perform mixed crop-livestock farming largely depend on the ES these three major land use types provide. Smallholders in the region are highly diverse in terms of resource endowments such as land and water. The generally huge yield gaps (with yield levels at 20% of the attainable), food insecurity and shrinking land holdings call for radical changes in land use policies and management to avoid societal unrest growing in the future. In national plans on sustainable development, sustainable intensification (Cassman & Grassini, 2020) of these systems, not surprisingly, has the highest policy priority (Sikora et al., 2020). It is seen as an important means to provide incentives to the younger farmer generation, boost agricultural development and to set land aside for nature conservation. A broad range of management interventions has been suggested for promoting sustainable intensification (Cassman & Grassini, 2020), including cereal intercropping with legumes, site-specific fertilizer application and irrigation. Most experimental studies on testing such interventions have just looked at impacts on dry matter production and yield, but a few also looked at other ecosystem functions such as carbon sequestration and water and nutrient use efficiency. Yet, to date, no study has looked in an integrated manner at the complexity of smallholder systems with a broad range of interacting ES at the landscape level. There is an urgent need to develop and apply an appropriate analytical framework to assess the current status of ecosystems and their functions. Land management interventions must be identified that can reverse the decline of ES and work toward the achievement of the SDGs in the face of climate change and other global change processes such as population growth and biodiversity decline. Received: 20 January 2021 Accepted: 25 February 2021