A study led by Chilean geographer at the University of Oxford, Alejandra Mora, integrated satellite detection, drone imaging, and Google Earth Engine technology to create a global platform for these seaweeds. The research was published in the journal Remote Sensing.
Andrea Navarro, IDEAL Center. The huiro (seaweed), whose scientific name is Macrocystis pyrifera, is a species of macroalgae widely distributed on the planet, which forms underwater forests and houses one of the richest and most productive ecosystems on Earth. It can measure up to 70 meters long, almost doubling the length of the blue whale and, under optimal conditions, reaches growth rates of up to about 50 cm daily.
There are records of places like Tasmania, where these forests have practically disappeared entirely due to the effects of climate change. In other areas of its distribution, such as in Baja California, increases in average sea temperatures have caused a depression of these ecosystems without the option of full recovery. As a result, studying them becomes essential, especially considering the enormous amount of ecosystem services they provide to humans (especially as supporters of various fisheries globally) and which are valued at billions of dollars.
Despite the fact that its forests provide refuge, food and reproduction for countless marine organisms and species, to date there has been no detailed information on their distribution in some regions, especially in the high latitudes of the Southern Hemisphere.
To fill this gap, a team of researchers, led by the Chilean geographer and candidate for a doctorate from the University of Oxford Alejandra Mora and in which scientists from the Center for Dynamic Research of High Latitudes Marine Ecosystems (IDEAL) of the Austral University of Chile (UACh) participated, created the first global high-resolution map of the distribution of the huiro forests.
The study, published in the scientific journal Remote Sensing, integrated various methodologies: satellite detection, drone images and Google Earth Engine technology. The latter facilitated the integration of thousands of satellite images in an algorithm that filtered the reflectance of the huiro between the coast and the ocean. All this was complemented with diving samplings carried out in Maitencillo, Niebla, Patagonian channels and fjords of the Aysén region, Strait of Magellan, Beagle Channel and Falklands islands, covering a latitudinal distance of 2,500 kilometers.
Thanks to this map, which condenses satellite images from 2015 to 2019, scientists will be able to address new questions related to the distribution and connectivity of these forests in the world ocean and their abundance dynamics.
“This tool will contribute to the environmental monitoring of the communities of huiros. Until now, most of the studies have focused on specific sectors, and this platform gives a global vision regarding the total extension of hectares and will allow long-term estimates to be made,” explains Mora.
One of the results of the investigation showed that, in the marine ecoregion of channels and fjords in southern Chile, the distribution of the forests of these brown algae reaches, according to a conservative estimate, 4,800 hectares. “The maps that we use in this investigation are oriented to the south, proposing a paradigmatic change in the observation of the planet. We wanted to highlight the oceanic character of the planet and its connectivity in the southern hemisphere,” adds Mora.
“The information gathered will help us understand whether this species is resilient against climate change and environmental stressors. What happens with the huiro forests has direct consequences not only in marine ecosystems, but also in human beings. For this reason, it is necessary to continue advancing and filling the information gaps that still exist, particularly in the extreme south of the American continent, ”says the IDEAL Center doctor candidate and co-author of the study, Mauricio Palacios, who is part of the research group led by Dr. Pirjo Houvinen, who has been working more than four years in the line of remote perception in southern ecosystems. At the end of 2019, his team provided the first background on huiro forests in the Yendegaia Fjord using these techniques.
Updated satellite imagery and dataset of the world’s huiro forest distribution is available online. Those who want to remotely explore the maps of this giant seaweed can do so from here.
Read scientific article here.