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Topic Name: Coral Disease Research Team say global warming is destroying coral reefs and calls for 'drastic actions'

Category: Environmental engineering

Research persons: Drew Harvell

Location: Coral Reef Targeted Research (CRTR), Australia

Details

If world leaders do not immediately engage in a race against time to save the Earth's coral reefs, these vital ecosystems will not survive the global warming and acidification predicted for later this century. That is the conclusion of a group of marine scientists from around the world in a major new study published in the journal Science on Dec. 13.
"It's vital that the public understands that the lack of sustainability in the world's carbon emissions is causing the rapid loss of coral reefs, the world's most biodiverse marine ecosystem," said Drew Harvell, Cornell professor of ecology and evolutionary biology and head of the Coral Disease Research Team, which is part of the international Coral Reef Targeted Research (CRTR) group that wrote the new study.

The rise of carbon dioxide emissions and the resultant climate warming from the burning of fossil fuels are making oceans warmer and more acidic, said co-author Harvell, which is triggering widespread coral disease and stifling coral growth toward "a tipping point for functional collapse."

The 17 marine scientists who authored the new study argue that "drastic action" is needed from world leaders to turn around the trend in rising levels of atmospheric carbon dioxide (CO2) to protect coral reefs. They based their conclusions on the forecasts for rising global temperatures and levels of CO2 announced recently by the Intergovernmental Panel on Climate Change, a United Nations body.

"Coral reefs have already taken a big hit from recent warm temperatures, but rapid rises in carbon dioxide cause acidification, which adds a new threat: the inability of corals to create calcareous skeletons," said Harvell. "Acidification actually threatens all marine animals and plants with calcareous skeletons, including corals, snails, clams and crabs. Our study shows that levels of CO2 could become unsustainable for coral reefs in as little as five decades."

In the short term, better management of overfishing and local stressors may increase resilience of reefs to climate threats, but rising global CO2 emissions will rapidly outstrip the capacity of local coastal managers and policy-makers to maintain the health of these critical ecosystems if the emissions continue unchecked, the authors stress.

At stake, added Ove Hoegh-Guldberg, director of the Center for Marine Studies at the University of Queensland, Australia, and the study's senior author, are ecosystems that play vital roles in providing habitats for a vast array of marine species that are essential to the oceans' complex food chain. They also provide livelihoods to 100 million people who live along the coasts of tropical developing countries. Diving tourism in the Caribbean alone is estimated to generate more than $100 billion a year. The loss of coral reef ecosystems also is exposing people to flooding, coastal erosion and the loss of food and income from reef-based fisheries and tourism, he added.

The CRTR is a leading international coral reef research initiative that provides a coordinated approach to credible, factual and scientifically proven knowledge for improved coral reef management. It is a partnership of the Global Environment Facility, the World Bank, the University of Queensland, Australia, the U.S. National Oceanic and Atmospheric Administration and approximately 40 research institutes and other third parties around the world.

Note for Coral reef

Coral reefs are aragonite structures produced by living organisms, found in shallow, tropical marine waters with little to no nutrients in the water. High nutrient levels such as that found in runoff from agricultural areas can harm the reef by encouraging the growth of algae. In most reefs, the predominant organisms are stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate (limestone). The accumulation of skeletal material, broken and piled up by wave action and bioeroders, produces a massive calcareous formation that supports the living corals and a great variety of other animal and plant life. Although corals are found both in temperate and tropical waters, reefs are formed only in a zone extending at most from 30°N to 30°S of the equator; although the reef-forming corals do not grow at depths of over 30 m (100 ft) temperature has less of an effect on distribution but it is generally accepted that no corals exist in waters below 18 °C.

Note for Global warming

Global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.
The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 year period ending in 2005, which is higher than the earlier estimate of 0.6 ± 0.2 °C for the period ending in 2000. The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations" via the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward. These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. While individual scientists have voiced disagreement with some of the main conclusions of the IPCC, the overwhelming majority of scientists working on climate change are in agreement with them.
Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century. The range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a millennium even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.
Increasing global temperature will cause sea level to rise, and is expected to increase the intensity of extreme weather events and to change the amount and pattern of precipitation. Other effects of global warming include changes in agricultural yields, trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors.
Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. There is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences. Most national governments have signed and ratified the Kyoto Protocol, aimed at reducing greenhouse gas emissions.

Picture overview

Pictured at left is the typical coral reef today on the southern Great Barrier Reef, which has endured a rise of 1 degree C and 375 parts per million of atmospheric carbon dioxide concentration. The middle frame shows what a reef would look like if global temperatures rise one more degree and CO2 concentrations increase, as predicted. The right frame shows what a reef would like if temperatures and CO2 levels rise even more.