Impact of terrestrial erosion on coral reef health at Bonaire: a plea for nature-inclusive "watershed-to-reef" based coastal management

Abstract

Coral reefs are rapidly degrading worldwide, due to a combination of global and local stressors. While global stressors, such as ocean warming, cannot be managed, management of local stressors can increase the resilience of coral reefs to these global stressors. One such local stressor is overgrazinginduced terrestrial erosion causing sediment and nutrient runoff to coastal waters, which is associated with coral mortality and changes in benthic community composition. In this study we assessed the link between watershed-specific erosion hazard and coral reef health, using the coral reefs on the west coast of Bonaire, Caribbean Netherlands, as a case study. We first identified watersheds, waterflow and runoff sites into the sea based on a digital elevation model. Next, for each watershed we determined the mean erosion hazard (a proxy for the degree of terrestrial runoff based on slope and ground vegetation cover). Subsequently, we used multiple regression models to investigate whether mean erosion hazard of the nearest upstream watershed, and distance to the nearest upstream runoff point explained variation in marine benthic community composition at two depth zones (~5 m and ~10 m). We found a negative relationship between mean erosion hazard and coral cover (a proxy for coral reef health) at 5 m depth, but no such effect at 10 m depth. In addition, we found a positive relationship between mean erosion hazard and sand cover (a proxy for sediment runoff) for both depth zones, and a small but significant quadratic effect of mean erosion hazard on algae cover (a proxy for nutrient runoff) at 5 m depth. Moreover, distance to the nearest upstream terrestrial runoff point was positively related with coral cover at 10 m depth, and negatively related with sand cover at 10 m depth. Our results provide direct evidence for a negative relationship between watershed-specific erosion hazard and coral reef health, and highlight the need for a nature-inclusive "watershed-to-reef" based coastal management approach that integrates terrestrial and marine conservation to preserve the island's valuable coral reef and related ecosystem services.

Inventory and characterization of food systems on Bonaire

“…Current intake of fruits and vegetables on Bonaire is lower than international recommendations for a healthy diet. Precise numbers of fruit and vegetable intake are not available, but intake has been estimated at 100 g per capita per day (Van Der Geest & Slijkerman, 2019). This is much lower than in the rest of the Netherlands which consumes on average 165 g vegetables per capita per day and 130 g fruits per capita per day (RIVM 12 ), while the national consumption guideline is to eat daily 200 g of fruits and 200 g of vegetables, which is in line with the guideline to eat daily 400 g fruits and vegetables by the World Health Organisation (WHO 13 ).…”

“…This means that it may be difficult to produce such vegetables economically on Bonaire. Estimates suggest that between 25 and 40% of the current annual fruit and vegetable consumption (879 ton, see before) can be produced locally (Van Der Geest & Slijkerman, 2019). This would mean that an annual production is needed between 220 and 352 t per year to meet current intake levels (Table 2).…”

Solar Energy Drier for Algae with Water Recovery for Island Applications

“…The interdependences in the Water, Food, Energy and Ecosystem security Nexus [1]. As Austen et al [2] demonstrate, ecosystem valuation must be considered as part of this approach that has to help the achievement of objectives and targets of the environmental policies such as the Good Environmental Status (GES) of the island riparian sea or ocean waters.…”

“…In the current context of the population growth, degradation of the habitat, the evolution of the accumulation of Green House Gases (GHG) in the atmosphere and trends in the climate change, the situation of the islands and especially of the small islands, is one of the most vulnerable. There are several approaches to address the complexity of the factors that are affecting of mid and long term the socio-economic situation of the islands and the water-food-energy-ecosystem security nexus approach, as [1] demonstrates, is a holistic and wellstructured one for their sustainable development.…”

Framework for a water quality monitoring program for the Caribbean Netherlands

“…In addition, coastal development, brine water discharge and free-roaming livestock are responsible for severe damage to land and vegetation, resulting in erosion with run-off during rain events, storm and wind reversals. These processes increased the overall pollution of coastal water in the form of increased nutrient and sediment levels and pathogens, resulting in reefs that are increasingly dominated by macro-algae and cyanobacteria (De Bakker et al, 2017;Van der Geest et al, 2020).…”