Quantifying the effects of spatial, temporal and social heterogeneity on ecological and socioeconomic functions
Ongoing research in EFForTS has demonstrated that land-use systems differ significantly in key ecolog-ical and socioeconomic functions (Focus 1). However, there is also a high degree of variability in the quantified functions within each land-use system (Guillaume et al. 2015, Teuscher et al. 2015) suggesting an important role of spatial, temporal and social heterogeneity. For instance, differences in soil quality, plant and tree age, stand structural attributes, spatial configuration and historical land use as well as social factors, local institutions such as land property rights, and access to markets and infrastructure may additionally affect ecological and socioeconomic variables measured for each land-use system (Bellemare et al. 2002, Tscharntke et al. 2005, Priess et al. 2007, Polasky et al. 2008, Nelson et al. 2009, Euler et al. 2017, Krishna et al. 2017, Kunz et al. 2017, Hein et al. 2016). Understanding the role of heter-ogeneity is thus key for understanding complex socio-ecological systems as a whole, for identifying win-win solutions of efficient, sustainable land-use management and for balancing human needs, biodi-versity conservation, and ecosystem functions and services in human-dominated landscapes (Naidoo and Ricketts 2006, Polasky et al. 2008, Bennett et al. 2009). In Focus 2 we study the effects of spatial, temporal and social heterogeneity on ecological and socioeconomic functions, which will directly con-tribute to the development of scaling functions in Focus 3.
In Phase 2, we have collaborated on a couple of multidisciplinary papers to integrate information related to environmental processes and biodiversity of different taxonomic groups. First, we have addressed the question how stand structural components affect species richness of different groups of organisms (Rembold et al. unpubl. data). Overall, we observed that there is a strong loss in structural complexity from forest to more uniform plantations and this is generally strongly linked to species loss. We further observed, however, that the response of individual taxonomic groups is highly variable. In a second contribution, where we analyse the effects of land-use change on species turnover, such highly variable response of biodiversity was also documented (Salecker et al. unpubl. data, Fig. 6). Furthermore, vari-ous scientific projects have analysed relationships between land property rights, agricultural input intensi-ty, biodiversity, environmental efficiency, productivity, and farm income in rubber an oil palm. Under-standing these relationships helps to explain ecological and socioeconomic heterogeneity.
A major novelty of Phase 2 was the establishment of riparian sites as major component of landscape heterogeneity. As part of the Core Plot Design of Phase 2, riparian areas have been investigated by most of the projects of Project Groups A and B. First results suggest that riparian sites may significantly contribute to animal diversity, with the effect being most pronounced in semiaquatic taxa such as amphibi-ans in particular in rainforest which contrasts earlier studies (Paoletti et al. 2018). By contrast, the diversi-ty of other taxa such as birds and reptiles differed little between upland and riparian sites (Fig. 1), but this needs more detailed analysis which are ongoing.
Fig. 1. Differences between riparian and upland sites tend to be greater for forests than plantations.
Shown are species richness of amphibians, reptiles, birds, fungi (soil and root communities) and soil arthropods, as well as aboveground biomass (AGB) and harvested biomass (yield) across tropical land uses on upland and ripar-ian plots. Polygon nodes indicate mean values (scaled between 0 and 100%) of eight study plots per land-use system and flooding regime (Grass et al. unpubl. data).
Research combining socioeconomic data with satellite imageries on historical land use showed how im-portant formal land titles are for farmers’ decisions to intensify production and increase the yield levels on the area that is already cultivated. Higher yields decrease farmers’ incentives to encroach additional forestland, which underlines the important relationships between land property rights, deforestation, and related land-use changes (Kubitza et al. 2018a). Other research showed temporal heterogeneity in the economic effects of land use depending on international price developments, which can entail further land-use change. The low rubber prices in 2015 have increased the relative profitability of oil palm culti-vation and have thus provided additional incentives to expand the oil palm area in Jambi (Kubitza et al. 2018b). Heterogeneity in the social effects of land-use change was also analysed for different types of households, including farm and non-farm households. While the expansion of the oil palm area increases income inequality among farming households, it tends to decrease inequality among non-farm house-holds due to labor market effects (Bou Dib et al. 2018a, b). Our research also shows that it is important to tailor policy interventions to heterogeneous socio-economic conditions (Rudolf et al. 2019). In villages with good market access, simple information campaigns significantly increased native tree planting among oil palm farmers, whereas in villages with poor market access additional structural interventions where necessary to induce similar levels of tree planting. A synthesis paper is in progress that aims at combining data from different C-projects (C07 Qaim, C08 Wollni, C04 Klasen/Lay) to study the effects of spatial and social heterogeneity on oil palm management decisions and yields to derive policy recom-mendations that take heterogeneity explicitly into account.
In Phase 3, the ecological projects will continue to investigate the different land-use systems within EF-ForTS Core Plot Design that are nested within farm, community and landscape levels. This research will generate data on temporal and spatial heterogeneity in ecological and socioeconomic functions allowing more complex and comprehensive analyses and conclusions. Likewise, the continuation of data collec-tion in the socioeconomic projects will generate time series and panel data at plot, farm, household, and village levels, which will allow in-depth analyses of how socioeconomic functions vary in space and time dependent on the social context. In Phase 3, the EFForTS-OPMX (see above), which experimentally var-ies the land-use intensity of oil palm plantations, and the EFForTS-BEE (B11 Hölscher/Kreft/Wollni, see above), which consists of varying levels of tree diversity in oil palm plantations, will generate more data to understand sources and implications of heterogeneity within oil palm. Finally, the novel Landscape Assessment planned in Phase 3 is designed to cover more heterogeneity within land-use systems. Co-ordinated collection of ecological and socio-economic data from 100 new study plots and the associat-ed land-owners will allow us to analyse how heterogeneity across different ecological and socioeconom-ic functions is correlated within and across land-uses. Overall, Focus 2 investigates the following three Hypotheses:
- Ecological and socioeconomic functions of a given land-use system differ between landscapes, over time and by social context, i.e. statistically there are interaction effects between ecological and socioec-onomic factors not only across but also within a particular land-use system.
- Within land-use systems, there are large differences in profitability, risk, biodiversity and ecological functions between farms and over time, and these can be explained by differences in the ecological and socioeconomic setting and/or management practices of the farm.
- Heterogeneity in local, regional, national and international economic and institutional conditions af-fects land-use change and management, and associated implications for biodiversity and ecological functions.