The Urgent Wake-Up Call: Fourth Global Coral Bleaching Event
The fourth global coral bleaching event, announced this week, is an urgent wake-up call to the world.
Introduction
The US National Oceanographic and Atmospheric Administration’s announcement of the fourth global coral bleaching event is a significant development. This event marks the second global mass bleaching in the past decade, indicating a new reality of more frequent and severe bleaching events due to rising ocean temperatures.
Shorter Recovery Windows and Widespread Stress Events
Cycles of decline and recovery are normal for coral reefs, but the windows for recovery are now shorter. Stress events such as marine heatwaves are occurring more rapidly and with less warning. Additionally, these events are becoming more widespread.
The latest global sea surface temperatures remain above long-term averages. As the southern hemisphere enters winter and the northern hemisphere’s tropical oceans enter summer, heat will accumulate from a higher base. Reefs are expected to experience greater heat stress earlier than in previous years.
What Happened Last Summer?
Widespread mass bleaching is a relatively new phenomenon for coral reefs, with the first global bleaching event occurring in 1998. These events are declared when significant coral bleaching is confirmed in the Atlantic, Indian, and Pacific oceans.
The current event is shaping up to be one of the most severe yet. It began with severe heat stress accumulating in the northern hemisphere summer of 2023 and continued into the southern hemisphere summer of 2023-24. Ocean temperatures now remain higher for longer periods, with maximums above historic values extending into April.
On the Great Barrier Reef, large areas experienced record-breaking heat stress over the summer, resulting in prevalent bleaching on three-quarters of surveyed coral reefs in shallow water.
Why Are Coral Reefs Important?
Coral reefs play a vital role in ocean health and provide food, income, and coastal protection for millions of people. Despite covering less than 1% of the seafloor, they support at least 25% of marine species. However, coral reefs are highly vulnerable to the effects of climate change, particularly increasing concentrations of greenhouse gases that are heating the oceans.
Can Reefs Recover from This Event?
The full impacts of the current global bleaching event are still unfolding and will not be known for some time. Some coral deaths are immediate, while others may recover or succumb after the ocean heat subsides. The responses of corals to heat stress and their recovery after an event vary depending on local and species-specific factors.
Bleaching occurs when corals under severe stress expel the symbiotic algae living in their tissues, causing them to turn completely white. While not dead, bleached corals are weakened and more susceptible to diseases. Bleaching can also impair their capacity to reproduce.
Data analyzed by the Global Coral Reef Monitoring Network shows a downward trend in coral abundance between 2009 and 2018, reflecting the cumulative impacts of previous bleaching events and local pressures such as pollution, coastal development, and overfishing.
An Opportunity to Learn More About Saving Reefs
Mass coral bleaching events provide a unique opportunity for research to inform actions aimed at protecting and restoring coral reefs. Scientists are studying which corals are most tolerant of heat, whether corals are adapting to marine heatwaves, why corals recover differently, and how this knowledge can be used to improve reef resilience.
Long-term monitoring is crucial for identifying areas of coral reefs that recover naturally after a disturbance and areas that do not. This information helps guide reef managers and scientists in focusing their efforts on reef protection and recovery. Recent monitoring innovations will improve access to quality data in the medium term.
What Can We Do?
The speed at which the world acts to reduce greenhouse gas emissions will determine the future of reefs, marine species, and ecosystem functions and services. A multi-pronged approach for protecting and restoring coral reefs, focusing on local and regional actions and solutions, has guided many management strategies and calls to action worldwide.
Science plays a crucial role in finding cost-effective solutions to improve reef resilience. Tackling local factors affecting coral reef health, implementing innovations for protection and restoration, and taking urgent action to curb the effects of global climate change are vital for the health of our oceans and the millions of people who depend on marine resources.
SDGs, Targets, and Indicators
SDG 13: Climate Action
- Target 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning.
- Indicator 13.3.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning into primary, secondary, and tertiary curricula.
SDG 14: Life Below Water
- Target 14.2: Sustainably manage and protect marine and coastal ecosystems to avoid significant adverse impacts, including by strengthening their resilience and taking action for their restoration in order to achieve healthy and productive oceans.
- Indicator 14.2.1: Proportion of national exclusive economic zones managed using ecosystem-based approaches.
SDG 15: Life on Land
- Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements.
- Indicator 15.1.1: Forest area as a proportion of total land area.
SDG 17: Partnerships for the Goals
- Target 17.16: Enhance the global partnership for sustainable development, complemented by multi-stakeholder partnerships that mobilize and share knowledge, expertise, technology, and financial resources.
- Indicator 17.16.1: Number of countries reporting progress in multi-stakeholder development effectiveness monitoring frameworks that support the achievement of the sustainable development goals.
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Source: theconversation.com
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