Spatial planning for a green economy: National-level hydrologic ecosystem services priority areas for Gabon

Abstract

Rapidly developing countries contain both the bulk of intact natural areas and biodiversity, and the greatest untapped natural resource stocks, placing them at the forefront of “green” economic development opportunities. However, most lack scientific tools to create development plans that account for biodiversity and ecosystem services, diminishing the real potential to be sustainable. Existing methods focus on biodiversity and carbon priority areas across large geographies (e.g., countries, states/provinces), leaving out essential services associated with water supplies, among others. These hydrologic ecosystem services (HES) are especially absent from methods applied at large geographies and in data-limited contexts. Here, we present a novel, spatially explicit, and relatively simple methodology to identify countrywide HES priority areas. We applied our methodology to the Gabonese Republic, a country undergoing a major economic transformation under a governmental commitment to balance conservation and development goals. We present the first national-scale maps of HES priority areas across Gabon for erosion control, nutrient retention, and groundwater recharge. Priority sub-watersheds covered 44% of the country’s extent. Only 3% of the country was identified as a priority area for all HES simultaneously, highlighting the need to conserve different areas for each different hydrologic service. While spatial tradeoffs occur amongst HES, we identified synergies with two other conservation values, given that 66% of HES priority areas intersect regions of above average area-weighted (by sub-watersheds) total forest carbon stocks and 38% intersect with terrestrial national parks. Considering implications for development, we identified HES priority areas overlapping current or proposed major roads, forestry concessions, and active mining concessions, highlighting the need for proactive planning for avoidance areas and compensatory offsets to mitigate potential conflicts. Collectively, our results provide insight into strategies to protect HES as part of Gabon’s development strategy, while providing a replicable methodology for application to new scales, geographies, and policy contexts.

Landscapes, at your service: applications of the Restoration Opportunities Optimization Tool (ROOT)

“…Hydrological ecosystem services refer to the benefits to people produced by the effects of terrestrial ecosystems on freshwater resources (Brauman et al, 2007). They can be important for sustainable development through the supply of clean water, which can benefit human health, and for other uses of water such as irrigation, agriculture and the generation of hydroelectricity (Goldstein et al, 2017). The analysis of sediment runoff evaluated the contributions of the different restoration actions to soil retention, thereby reducing erosion and sediment export into streams and rivers (Fernández-Moya et al, 2014;Goldstein et al, 2017;Guerry et al, 2015;Tscharntke et al, 2011).…”

“…They can be important for sustainable development through the supply of clean water, which can benefit human health, and for other uses of water such as irrigation, agriculture and the generation of hydroelectricity (Goldstein et al, 2017). The analysis of sediment runoff evaluated the contributions of the different restoration actions to soil retention, thereby reducing erosion and sediment export into streams and rivers (Fernández-Moya et al, 2014;Goldstein et al, 2017;Guerry et al, 2015;Tscharntke et al, 2011). The nutrient retention analysis evaluated the role of restoration actions in removing a portion of the nitrogen and phosphorus contributed by fertiliser application, as well as the impact of a reduction in the use of fertilisers (Goldstein et al, 2017;Kovacs et al, 2013;Power, 2010;Scherr & McNeely, 2008).…”

“…In this study, with a focus on the restoration of agricultural production systems, the main sources of nutrients considered are the application of fertilisers, livestock manure and vegetation (litter and crop residues, among others). The restoration actions modelled will impact both the amounts of additional nutrients, such as a reduction in the application of synthetic fertiliser, and the ability of ecosystems to retain or filter excess nutrients before they reach downstream water bodies (Goldstein et al, 2017;Kovacs et al, 2013;Sharp et al, 2016). Once the nutrients reach a body of water, the model does not assume any additional retention or removal (Kovacs et al, 2013).…”

“…However, Goldstein et al (2017) in their restoration prioritisation analysis defined priority areas for hydrological ecosystem services as those areas that provide the highest levels of water quantity and quality benefits to people. The changes modelled with InVEST can result in different kinds of human impacts, such as a decrease in the cost of drinking water purification or an increased reservoir capacity due to reduced siltation (Lele, 2009).…”

“…Erosion control is an important ecosystem service for the hydropower sector, since higher sediment concentrations in streams decrease electricity production (Goldstein et al, 2017;Vogl et al, 2016). As priority areas for the reduction in sediment export, those parts of sub-watersheds that flow to the water catchment points of the Costa Rican hydroelectricity plants are included in the spatial analysis (Figure 33a).…”