DOI: 10.5061/dryad.r9n52
title: Data from: Seagrass on the brink: decline of threatened seagrass Posidonia australis continues following protection

description: Seagrasses are in decline globally due to sustained pressure from coastal
 development, water quality declines and the ongoing threat from climate
 change. The result of this decline has been a loss of coastal
 productivity, a reduction in critical fisheries habitat and increased
 erosion. Attempts to slow this decline have included legislative
 protection of habitat and direct restoration efforts. Monitoring the
 success of these approaches requires tracking changes in the abundance of
 seagrasses, but such monitoring is frequently conducted on large scales
 that lack the sensitivity to detect changes in time. Here, we used high
 resolution aerial imagery to quantify the change in meadows dominated by
 Posidonia australis over five years at 14 sites in five estuaries in
 south-eastern Australia. Australia has some of the world's most
 diverse and extensive seagrass meadows, but the widely distributed P.
 australis has a slow growth rate, recovers poorly after disturbance, and
 suffers runaway attrition if the conditions for recovery are not met. In
 2010, after declines of 12-57% between the 1940s and 1980s, P. australis
 was listed as a threatened ecological community in New South Wales. We
 quantified changes in area at fine scales and, where loss was observed,
 describe the general patterns of temporal decline within each meadow. Our
 results demonstrate that seagrass meadows dominated by P. australis
 underwent declines of ~ 2-40% total area at our study sites between 2009
 and 2014. In the iconic Sydney Harbour, our analyses suggest that P.
 australis meadows are declining at an average rate greater than 10% yr-1,
 exceeding the global rate of seagrass decline. Highlighting these alarming
 declines across the study region should serve as means to prioritise
 management action and review the effectiveness of legislative listing as a
 method to limit impacts at an ecosystem level.
description: Point sampling
 dataData generated from
 point-sampling aerial imagery to obtain an estimate of seagrass cover over
 timePoint
 sampling.xlsxBalgowlah
 shapefilesShapefiles and images
 for the Posidonia australis meadow located at site 'Balgowlah'
 (BG) in Sydney HarbourBalgowlah.zipBarrenjoey Head ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Barrenjoey Head' (BH) in PittwaterBarrenjoey Head.zipBurraneer Bay ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Burraneer Bay' (BB) in Port HackingBurraneer Bay.zipDolans Bay ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Dolans Bay' (DB) in Port HackingDolans Bay.zipGunnamatta Bay ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Gunnamatta Bay' (GB) in Port HackingGunnamatta Bay.zipKurnel East ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Kurnell East' (KE) in Botany BayKurnel East.zipKurnel West ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Kurnell West' (KW) in Botany BayKurnel West.zipManly Wharf ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Manly Wharf' (MW) in Sydney HarbourManly Wharf.zipMarks Point ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Marks Point' (MP) in Lake MacquarieMarks Point.zipPalm Beach ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Palm Beach' (PB) in PittwaterPalm Beach.zipQuibray Bay ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Quibray Bay' (QB) in Botany BayQuibray Bay.zipSeaplane Wharf ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Seaplane Wharf' (SW) in PittwaterSeaplane Wharf.zipYacht Club North ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Yacht Club North' (YN) in Lake MacquarieYacht Club North.zipYacht Club South ShapefilesShapefiles and images for the Posidonia australis meadow located at site 'Yacht Club South' (YS) in Lake MacquarieYacht Club South.zipBefore-After polygon attributesData generated from shapefiles to compare seagrass meadow size (as polygons) in 2009/2010 and 2014