Climate change and its impact on the oceans
22 scientists from around the world—including Silliman University’s Hilconida Calumpong, Ph.D.—submitted to the UN General Assembly in late 2015 their report as the Ad Hoc Working Group on the Regular Process for Global Reporting and Assessment of the State of the Marine Environment, including Socioeconomic Aspects. Here are some excerpts:
Corals are subject to “bleaching” when the seawater temperature is too high: they lose the symbiotic algae that give coral its colour and part of its nutrients. Severe, prolonged or repeated bleaching can lead to the death of coral colonies. An increase of only 1°C to 2°C above the normal local seasonal maximum can induce bleaching. Many heat-stressed or bleached corals subsequently die from coral diseases.
Rising temperatures have accelerated bleaching and mass mortality during the past 25 years. The bleaching events in 1998 and 2005 caused high coral mortality at many reefs, with little sign of recovery. Global analysis shows that this widespread threat has
significantly damaged most coral reefs around the world. Where recovery has taken place, it has been strongest on reefs that were highly protected from human pressures. However, temperature increase is outpacing recovery.
Losses of coral reefs can have negative effects on fish production and fisheries, coastal protection, ecotourism and other community uses of coral reefs. Current scientific data and modeling predict that most of the world’s tropical and subtropical coral reefs, particularly those in shallow waters, will suffer from annual bleaching by 2050, and will eventually become functionally extinct as sources of goods and services. This will have not only profound effects on small island developing States and subsistence
fishermen in low-latitude coastal areas, but also locally significant effects even in major economies, such as that of the United States.
Captures of fish stocks at levels above maximum sustainable yield
Globally, the levels of capture fisheries are near the ocean’s productive capacity, with catches on the order of 80 million tons. Exploitation inevitably reduces total population biomass through removals. As long as the fish stock can compensate through increased productivity because the remaining individuals face less competition for access to food and therefore grow faster and produce more progeny, then fishing can be sustained. However, when the rate of exploitation becomes faster than the stock can compensate through increasing growth and reproduction, the removal level becomes unsustainable and the stock declines.
The concept of “maximum sustainable yield” (is) entrenched in international legal instruments such as the UN Convention on the Law of the Sea.
At present, about a quarter of all assessed fish stocks are being overfished and more are still recovering from past overfishing. This is undermining the contribution that they could make to food security. Ending overfishing is a precondition for allowing stocks to rebuild. Other stocks may still be categorized as “fully exploited” despite being on the borderline of overfishing. Those could produce greater yields if effectively managed.
There are only a few means available to increase yields. Ending overfishing, eliminating illegal, unreported and unregulated fishing, bringing all fishery yields under effective management and rebuilding depleted resources may result in an increase of as much as 20 per cent in potential yield, provided that the transitional economic and social costs of rebuilding depleted stocks can be addressed.
Overfishing can also undermine the biodiversity needed to sustain marine ecosystems. Without careful management, such impacts on biodiversity will endanger some of the most vulnerable human populations and marine habitats around the world, as well as threaten food security and other important socioeconomic aspects (such as livelihoods). – Excerpted by SU Research and Environmental News Service