Crisálida apresenta a quarta reportagem de um dossiê de cinco artigos sobre o branqueamento e a morte dos corais no mundo todo.
A primeira postagem é a divulgação pela ONU de um trabalho coordenado por Ruben van Hooidonk, intitulado “Local-scale projections of coral reef futures and implications of the Paris Agreement”. Nature, Scientific Reports, 6, published online 21/XII/2016. (<http://www.nature.com/articles/srep39666>).
A segunda postagem trata da morte de mais de 70% do maior recife de coral no Japão no último verão setentrional. Veja <http://crisalida.eco.br/mais-de-70-do-maior-recife-de-coral-do-japao-morreu-em-2016/>
A terceira postagem relata como um experimento realizado no ano passado por Ken Caldeira e colegas confirma o impacto da acidificação dos oceanos sobre os corais. Veja
Esta quarta postagem mostra a evolução dos eventos de branqueamento desde os anos 1980 e discute em particular o advento do grande branqueamento e morte dos corais em 2015-2016.
A consortium of ocean scientists, reef mappers and community-based monitoring teams has confirmed that a “global coral bleaching event” is underway. Increased ocean temperatures due to climate change, combined with the warming effects of an El Niño pattern and a warm water mass in the Pacific referred to as “The Blob”, are driving temperatures to record levels – threatening to severely deplete coral reef ecosystems that support fish habitats, shoreline protection and coastal economies.
This global event – only the third of its kind in recorded history – is expected to impact roughly 38% of the world’s coral reefs by the end of this year and kill over 12,000 square kilometres (4,633 sq miles) of reefs, according to the National Oceanic and Atmospheric Administration (NOAA). Although reefs represent less than 0.1 percent of the world’s ocean floor, they help support 25 percent of all marine species. As a result, the livelihoods of 500 million people and income worth over $30 billion are at stake.
The declaration of the 2015-16 global coral bleaching event was confirmed by NOAA after its bleaching predictions were verified by scientists and citizen scientists in the Atlantic and Caribbean basin, including rapid response surveying teams from the XL Catlin Seaview Survey, the University of Queensland and Reef Check. These reports added to the growing list of reports in the Pacific and Indian Oceans.
Earth’s oceans absorb 93 percent of the increase in the planet’s heat from climate change, making them one of the most visual indicators of the issue – particularly when change is revealed through dramatic episodes like global coral bleaching. During a bleaching event, corals expel the golden-brown algae that grow within their body tissue, exposing their white skeletons; hence the term “bleaching.” If the ocean temperature remains higher than the seasonal norm for a number of weeks, the corals can die en masse, causing the loss of some corals that may be centuries old.
Bleaching can transform healthy coral reefs into reefs dominated by other organisms such as seaweeds. This can take decades to reverse and will only happen if conditions become hospitable for corals again.
Caused by unusual warming of the Northern Hemisphere oceans, 2015 has now seen coral bleaching occur in reefs in the northern Pacific, Indian, equatorial Pacific, and western Atlantic Oceans. Recorded for the first time in 1998 and again in 2010, global coral bleaching is declared when all three major ocean basins (Indian, Pacific, Atlantic) have recorded widespread bleaching episodes across multiple reefs spanning 100 km (62 miles) or more.
The first two global bleaching events were observed due to a chain of warming events caused by El Niño cycles and increased ocean temperatures resulting from climate change. This year’s widespread bleaching shows the same characteristics – warmer-than-usual water temperatures combined with what could potentially be the strongest El Niño ever recorded.
Coral bleaching in the Pacific Ocean began in mid-2014 and has not stopped since, moving around as warm conditions have enveloped different regions. With forecasts of the El Niño remaining strong into 2016, the worst may be yet to come.
During the global coral bleaching event of 1997-98, the world simply didn’t have the technology, understanding, or teams in place to reveal and record such events properly. However, recent advancements in bleaching prediction and near-real-time satellite monitoring have allowed scientists to deploy a rapid response team to capture images of coral bleaching as it happens.
Primed for immediate deployment to locations where major coral bleaching is taking place, XL Catlin Seaview Survey’s Rapid Response team uses their advanced SVII camera and other technologies to gather visual and other data of bleaching. The revolutionary camera system is attached to an underwater scooter that takes 1,000 high-resolution, 360-degree underwater images across distances of up to 2 kilometres (1.2 miles) in a single dive – increasing the team’s data-gathering efficiency 30-fold compared to previous methods. These images are added to an online research tool that allows scientists and resource managers to better analyse and monitor changes in reef ecosystems on a local, regional, and global level. The data collected will also help research teams advance their understanding of coral recovery and support future restoration efforts.
“This is only the third time we’ve seen a global-scale bleaching event,” said Dr. Mark Eakin, NOAA Coral Reef Watch coordinator. “What really has us concerned is this event has been going on for over a year and is likely to last another year.”
“Just like in 1998 and 2010, we’re observing bleaching on a global scale, which will cause massive loss of corals. With hundreds of millions of people relying on fisheries and reefs for sustenance, the repercussions of a global coral bleaching event could be potentially disastrous,” said Professor Ove Hoegh-Guldberg, the Survey’s chief scientist from the University of Queensland. “Through accurate coral reef mapping, monitoring and recovery initiatives worldwide, we have been able to study and understand the destructive effects of coral bleaching. We are now continuing our efforts to support these activities and create the foundations for a truly global call for action to protect these vital ecosystems.”
The world has lost roughly half of its coral reefs since the early 1980s. Hoegh-Guldberg says the current trend is directly in line with predictions he made in 1999 that continued global temperature rise would lead to the complete loss of coral reefs by the middle of this century.
“It’s certainly on that road to a point about 2030 when every year is a bleaching year,” he says. “So unfortunately I got it right.”