A predictive model based on multiple coastal anthropogenic pressures explains the degradation status of a marine ecosystem: Implications for management and conservation

Abstract

During the last fifty years, there has been a dramatic increase in the development of anthropogenic activities, and this is particularly threatening to marine coastal ecosystems. The management of these multiple and simultaneous anthropogenic pressures requires reliable and precise data on their distribution, as well as information (data, modelling) on their potential effects on sensitive ecosystems. Focusing on Posidonia oceanica beds, a threatened habitat-forming seagrass species endemic to the Mediterranean, we developed a statistical approach to study the complex relationship between human multiple activities and ecosystem status. We used Random Forest modelling to explain the degradation status of P. oceanica (defined herein as the shift from seagrass bed to dead matte) as a function of depth and 10 anthropogenic pressures along the French Mediterranean coast (1700 km of coastline including Corsica). Using a 50 x 50 m grid cells dataset, we obtained a particularly accurate model explaining 71.3 % of the variance, with a Pearson correlation of 0.84 between predicted and observed values. Human-made coastline, depth, coastal population, urbanization, and agriculture were the best global predictors of P. oceanica's degradation status. Aquaculture was the least important predictor, although its local individual influence was among the highest. Non-linear relationship between predictors and seagrass beds status was detected with tipping points (i.e. thresholds) for all variables except agriculture and industrial effluents. Using these tipping points, we built a map representing the coastal seagrass beds classified into four categories according to an increasing pressure gradient and its risk of phase shift. Our approach provides important information that can be used to help managers preserve this essential and endangered ecosystem.

Editorial: Marine Aquaculture Impacts on Marine Biota

“…Marine aquaculture provides undoubted economic benefits and diverts a proportion of fishing pressure on wild stocks. However, it is known to strongly impact marine life (Tacon and Forster, 2003) with the Mediterranean region, which is densely populated and urbanized with a strong demand for seafood, especially sensitive to marine aquaculture pressures (Colloca et al, 2017;Holon et al, 2018). This awareness led the Center for Mediterranean Cooperation of the International Union for Conservation of Nature to set up a working group in 2004.…”

Marine Aquaculture Impacts on Marine Biota

“…Marine aquaculture provides undoubted economic benefits and diverts a proportion of fishing pressure on wild stocks. However, it is known to strongly impact marine life (Tacon and Forster, 2003) with the Mediterranean region, which is densely populated and urbanized with a strong demand for seafood, especially sensitive to marine aquaculture pressures (Colloca et al, 2017;Holon et al, 2018). This awareness led the Center for Mediterranean Cooperation of the International Union for Conservation of Nature to set up a working group in 2004.…”

“…The recovery times of Posidonia oceanica meadows is in the order of at least decades and may be more than a century, so that losses can be considered to be irreversible at human time scales (Molinier and Picard, 1952;Boudouresque and Meinesz, 1982;Boudouresque et al, 2009. According to Holon et al (2018), the tipping point (shift from a healthy P. oceanica meadow to a significantly degraded meadow) is situated, on average, 320 m from a fish farm. A safety distance of 400 m has been suggested between fish farms and the nearest P. oceanica meadow .…”

Impacts of Marine and Lagoon Aquaculture on Macrophytes in Mediterranean Benthic Ecosystems

“…The recovery times of Posidonia oceanica meadows is in the order of at least decades and may be more than a century, so that losses can be considered to be irreversible at human time scales (Molinier and Picard, 1952;Boudouresque and Meinesz, 1982;Holmer et al, 2003;Boudouresque et al, 2009. According to Holon et al (2018), the tipping point (shift from a healthy P. oceanica meadow to a significantly degraded meadow) is situated, on average, 320 m from a fish farm. A safety distance of 400 m has been suggested between fish farms and the nearest P. oceanica meadow (Holmer et al, 2008).…”