DOI: 10.5061/dryad.g4f4qrfqq
title: Global sediment export based on InVEST Sediment Delivery Ratio model

description: Sediment runoff from disturbed coastal catchments is a major threat to
 marine ecosystems. Understanding where sediments are produced and where
 they are delivered enables managers to design more effective strategies
 for improving water quality. In this context, targeted restoration of
 degraded terrestrial areas provides opportunities to reduce land-based
 runoff from coastal areas and consequently foster coral reef conservation.
 To do this strategically, a systematic approach is needed to identify
 watersheds where restoration actions will provide the highest conservation
 benefits for coral reefs. This dataset is associated with the
 article "Global forest restoration opportunities to foster coral reef
 conservation", where we developed a systematic approach for
 identifying global forest restoration opportunities that would also result
 in large decreases in the flux of sediments to coral reefs. The dataset
 presented here consists of a global sediment export layer
 produced using the Sediment Delivery Ratio model of InVEST.
description: The sediment export per pixel is calculated using the soil
 erosion per pixel, as well the amount of sediment eroded from each pixel
 that actually reaches a stream or similar water course (Hamel et al.
 2015). To model soil erosion, we used a high-resolution global potential
 soil erosion model developed by Borrelli et al. (2017) based on the
 revised universal soil loss equation (RUSLE; Renard et al. 1997),
 estimating soil erosion in each watershed. Sediment export was quantified
 using the InVEST sediment delivery model (Hamel et al. 2015), which
 implements a soil loss algorithm linked to the sediment connectivity
 algorithm proposed by Borselli et al. (2008). More details about the
 methodological approach can be found in Suárez-Castro et al.
 (2021). Following Borrelli et al, we have capped the
 sediment export values to a maximum of 325 tonnes per hectare per year
 for pixels classified as barren, 250 tonnes per hectare per year for
 pixels classified as agricultural land and 50 tonnes per hectare per year
 for pixels classified as forest.  
description: Although substantial variations in model performance exist across
 regions, there is a high correlation between observations and predictions
 for 58 out of 65 basins used for the model calibration (We only calibrated
 our model for coastal basins having an effect on coral reefs). In
 addition, our model showed good agreement with the spatial patterns of the
 soil erosion model presented by Borrelli et al. (2017) (Spearman
 correlation coefficient of 0.91, Suarez-Castro et al. 2021) for all the
 studied regions. Even though the
 number of basins available for model validation was low, the good fit with
 Borrelli’s erosion model provides confidence that our model was able to
 correctly identify high and low sediment export areas at global
 scales. Our aim was to generate estimates
 that allow us to optimally capture relative differences and opportunities
 among watersheds, rather than describing fine-scale within watersheds
 processes. This modelling approach is thus suitable for our study as it
 allowed us to capture major differences between sub-watersheds that can
 help to identify hotspots of higher sediment export where priority actions
 should focus. However, pixel level estimates should be taken with caution,
 and calibration with localised data would be ideal if this dataset is used
 in local scale studies.