Long-term declines and recovery of meadow area across the world's seagrass bioregions

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Dunic, Jillian C
Brown, Christopher J
Connolly, Rod M
Turschwell, Mischa P
Côté, Isabelle M
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2021
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Abstract

As human impacts increase in coastal regions, there is concern that critical habitats that provide the foundation of entire ecosystems are in decline. Seagrass meadows face growing threats such as poor water quality and coastal development. To determine the status of seagrass meadows over time, we reconstructed time-series of meadow area from 175 studies that surveyed 547 sites around the world. We found an overall trajectory of decline in all 7 bioregions with a global net loss of 5602 km2 (19.1% of surveyed meadow area) occurring since 1884. Declines have typically been non-linear, with rapid and historical losses observed in several bioregions. The greatest net losses of area occurred in four bioregions (Tropical Atlantic, Temperate Northern Atlantic East, Temperate Southern Oceans, and Tropical Indo-Pacific), with declining trends being the slowest and most consistent in the latter two bioregions. In some bioregions, trends have recently stabilised or reversed. Losses, however, still outweigh gains. Despite consistent global declines, meadows show high variability in trajectories, within and across bioregions, highlighting the importance of local context. Studies identified 12 different drivers of meadow area change, with coastal development and water quality as the most commonly cited. Overall, however, attributions were primarily descriptive and only 10% of studies used inferential attributions. Although ours is the most comprehensive dataset to date, it still represents only one-tenth of known global seagrass extent, with conspicuous historical and geographic biases in sampling. It therefore remains unclear whether the bioregional patterns of change documented here reflect changes in the world's unmonitored seagrass meadows. The variability in seagrass meadow trajectories, and the attribution of change to numerous drivers, suggest we urgently need to improve understanding of the causes of seagrass meadow loss if we are to improve local-scale management.

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Global Change Biology

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27

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17

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DP180103124

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© 2021 The Authors. Global Change Biology published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Subject

Marine and estuarine ecology (incl. marine ichthyology)

Biological oceanography

Environmental sciences

Biological sciences

attribution

coastal ecosystems

global change

meta-analysis

reconstruction

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Dunic, JC; Brown, CJ; Connolly, RM; Turschwell, MP; Côté, IM, Long-term declines and recovery of meadow area across the world's seagrass bioregions, Global Change Biology, 2021, 27 (17), pp. 4096-4109

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