observed

A prolonged and widespread coral bleaching event in Australia’s Great Barrier Reef has taken place this year. It is the fifth such event over the past eight years and appears to be one of the worst ever. According to preliminary analysis, 97% of corals in some areas of the northern part of the reef died as a result of the bleaching. Over the entire length of the reef – which is more than 1,200 miles long – bleaching was observed on 74% of the more than 1,000 individual reefs that make up the Great Barrier Reef. Half of those observed recorded high or very high levels of bleaching, although less than 10% had extreme levels of bleaching.

Prior to this mass bleaching event, an extensive survey of the reef was conducted, and it provided some good news. Coral cover had increased in all three regions on the Great Barrier Reef and was actually at regional highs in two of the three regions. The surveys were completed before the passage of Tropic Cyclone Jasper in December 2023.

Bleached corals are very stressed, but they still remain alive for at least some period of time. Some types of corals can remain bleached for months, hanging on like a hospital patient in critical condition, but then recover. Depending upon water conditions going forward, it remains to be seen how much of the reef will survive the latest bleaching event. The next survey season by the Australian Institute of Marine Science will commence in September.

In many ways, the reef has had some lucky escapes in recent years. As marine heatwaves become increasingly common, its luck may eventually run out.

**********

Web Links

New report on Great Barrier Reef shows coral cover increases before onset of serious bleaching, cyclones

Photo, posted 8, 2023, courtesy of Chris Hoare via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Amazon is a source of many mysteries. One that was as troubling as it was mysterious was the large amounts of methane emissions coming from the rainforest that were observed by satellites but that nobody could find on the ground. In total, there were 20 million tons of methane whose origin was unknown.

An expedition by a British postdoctoral researcher who spent two months strapping gas-measuring equipment to thousands of trees has solved the mystery. It turns out that trees, especially in the extensive flooded forests, were stimulating methane production in the waterlogged soils and pumping it into the atmosphere.

This research has uncovered a previously-ignored major source of the second most important greenhouse gas in the world. Apparently, most of the world’s estimated 3 trillion trees emit methane at least some of the time.

This in no way implies that trees are bad for the climate and therefore should be cut down. The reality is that the carbon storage capability of trees far outweighs their methane emissions. But since corporations these days are planting trees to offset their carbon emissions, it is essential to know if their numbers add up. Carbon accounting has to include the complex chemistry of trees and methane.

Wetland tree trunks can act as passive conduits for methane generated by micro-organisms in waterlogged soils. The solid-looking trunks contain spaces and channels through which gases travel up and down. But in wetland systems, trees also create the conditions, and provide the raw materials, for methane generation by micro-organisms. Trees are essentially bioreactors. Some trees even actively generate methane from photochemical reactions in their foliage.

Understanding the interactions of ecosystems and the atmosphere is a complicated business.

**********

Web Links

Scientists Zero in on Trees as a Surprisingly Large Source of Methane

Photo, posted December 13, 2008, courtesy of Ivan Mlinaric via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Mixed news for the Great Barrier Reef

Web Links

Trees And Methane

Web Links