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Beagle kelp maps from: One of the least disturbed marine coastal ecosystems on Earth: Spatial and temporal persistence of Darwin’s sub-Antarctic giant kelp forests

Citation

Mora-Soto, Alejandra (2022), Beagle kelp maps from: One of the least disturbed marine coastal ecosystems on Earth: Spatial and temporal persistence of Darwin’s sub-Antarctic giant kelp forests, Dryad, Dataset, https://doi.org/10.5061/dryad.bcc2fqzck

Abstract

Aim: Marine habitats and their dynamics are difficult to systematically monitor, particularly those in remote locations. This is the case with the sub-Antarctic ecosystem of the giant kelp Macrocystis pyrifera, which was already noted by Charles Darwin in his accounts on the Voyage of the Beagle and recorded on the nautical charts made during that expedition. We combined these and other nautical charts from the 19th and early 20th centuries with surveys conducted in the 1970s and 1980s and satellite detection algorithms from 1984 to 2019, to analyse kelp distribution through time and the factors that correlate with it.

Location: Marine ecoregions of Channels and Fjords of Southern Chile, Falkland Islands (Malvinas), and the island of South Georgia.

Taxon: Macrocystis pyrifera.

Methods: We characterised 309 giant kelp forests by their coastal geospatial attributes. Statistically significant variables were included in a conditional inference tree to predict kelp forest size. Sea surface temperature (SST) records were analysed to confirm temperature ranges over the last four decades. Nautical charts, historical surveys, aerial photogrammetry, unmanned aerial vehicle (UAV) surveys and satellite imagery were overlaid to assess spatial distribution of kelp forest canopies, spanning the period 1829–2020.

Results: Considering the extensive natural and human caused changes over the last two centuries, this diverse kelp ecosystem is remarkably persistent. We found that the ocean currents and wave exposure, combined with the geomorphological settings of the coastline are the most critical factors predicting the extent of the kelp forests.

Main conclusions: We have described the long-term ecological persistence of the kelp forests in this vastly under-studied region that offers a conceptual biogeographical model supporting the global importance proposed by Charles Darwin 200 years ago (Darwin, 1845). In the current context of global change, the need for conservation of this persistent and well-preserved marine ecosystem has never been more important.

Usage Notes

Beagle Kelp project

BeagleKelpMaps and supplementary information

This is the repository of the original code https://biogeoscienceslaboxford.users.earthengine.app/view/beaglekelpcharts

You can explore and download the layers of this map here: https://code.earthengine.google.com/6d7a632defb18891908d337fea47746d

Kelp polygons (shapefiles) are in the file Beaglekelppolys.rar*

Multiyear maps:

Agua Fresca: https://code.earthengine.google.com/f22e097ee30487d882469307e31a78da

Goree Roads: https://code.earthengine.google.com/ebca06f9e3327d8c9e937a9e211aee54

Laredo: https://code.earthengine.google.com/3b2132982d155e5afc2df4ebae1251a6

Mitre: https://code.earthengine.google.com/7c2f3dc5f6af8658f6a933ca0938cbb2

Packsaddle Bay: https://code.earthengine.google.com/25302ce879990f84a4fd955dfe45f821

Wollaston: https://code.earthengine.google.com/95714101bc740acbb3df117652ea5e37

South Georgia: https://code.earthengine.google.com/b3dcd842b23666132b395f763a0110f4

Falkland Is. https://code.earthengine.google.com/b427f63c568243fbdfbcdb752fbfdf8f

Deseado: https://code.earthengine.google.com/adce87e83f2ed4e055da40eadafe57d1

 

*Beagle Kelp Polygons (shapefile)

Shapefile polygons covering the kelp forests drawn on UKHO nautical charts. 

Beagle_Key nomenclature:
1) The satellite-detected kelp areas covered the charted kelp in similar form and extent.
2) The satellite-detected kelp areas had spare pixels over the target kelp canopy: this may mean that the forest is small or with sparse fronds, largely undetected by the satellite sensor.
3) The satellite-detected kelp areas showed patterns not associated with kelp forests.
4) No satellite-detected kelp pixels over the targeted kelp.