Australia’s southern coastline is fringed with rocky reefs that support a seemingly endless forested canopy of the worlds largest seaweed, kelp. “The reef is inter-connected through oceanographic, ecological and evolutionary processes, and it supports critical energy and nutrient cycles that support the rich and diverse cool water marine habitats of the reef and the wider ocean beyond”.
These plants grow on sub-tidal rocky reefs. Some kelps are able to grow on smaller scattered rocks and or mollusk beds, and in general, they grow on reefs in waters that are generally cool and shallow. Kelp do not have roots. They attach themselves on rocks with claw like appendages called a holdfast. The point being that these appendages are exposed in the water and are now being devoured by sub-tropical grazers that have migrated to these forests. In a rapidly heating world, due to man made climate change, we may be seeing the demise of these forests not only in Australia but throughout the world as temperate eco-systems shift to sub-tropical and tropical eco-systems.
The world’s kelp forests.The ocean waters near the Kelp forests are among the fastest warming regions in the world. The water has become even more heated by a series of extreme heat waves over the past few years. The summer of 2011, caused temperatures to soar to highs not seen in 215 years of record keeping. Kelp can’t tolerate heat. They prefer much milder and cooler conditions. As a result, the kelp forests were destroyed by excessive warming much like Australia’s Great Barrier Reef by bleaching and the recent phenomenon of collapsing Mangrove forests caused by increasing salinity. If after a few years and the Kelp forest still has not rebounded, it may suggest that it will not be able to evolve quickly enough to avert disaster.
The Guardian reports:
Dr Thomas Wernberg, from the University of Western Australia’s oceans institute and lead author of the study, told the Guardian that 100km of kelp forest died following a marine heatwave in 2011 which saw the ocean temperature increase by 2C.
The death of the kelp caused the functional extinction of 370sq km of rocky cool-climate reefs, extending down the coast from Kalbarri, about 570km north of Perth, Western Australia.
The area was then rapidly colonised by turf-forming seaweeds and bottom-grazing tropical herbivores, such as rabbitfish and parrotfish, which stopped the kelp from regrowing.
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“It’s not just a matter of a temperate ecosystem being replaced by a tropical ecosystem... You sort of get locked into this intermediate stage where you have lots of small turf-forming seaweeds, so you lose the best parts of both systems.
From the Journal Science:
No turning back?
Ecosystems over time have endured much disturbance, yet they tend to remain intact, a characteristic we call resilience. Though many systems have been lost and destroyed, for systems that remain physically intact, there is debate as to whether changing temperatures will result in shifts or collapses. Wernburg et al. show that extreme warming of a temperate kelp forest off Australia resulted not only in its collapse, but also in a shift in community composition that brought about an increase in herbivorous tropical fishes that prevent the reestablishment of kelp. Thus, many systems may not be resilient to the rapid climate change that we face.
Science, this issue p. 169
Abstract
Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests.
Australia’s re-elected Prime Minister Malcolm Turnbull has scraped a victory with a tiny majority that will make delivery on the health of Australian reefs more difficult according to the Centre for Research on Globalization. Like Florida and North Carolina, it appears that uttering the words “Climate Change” in Australia is taboo.
Four weeks into the campaign and the Australian Department of Environment was caught removing all references to the Reef from a joint UNESCO (United Nations Educational, Scientific and Cultural Organisation), United Nations Environmental Program (UNEP), and Union of Concerned Scientists report on climate change and World Heritage sites. The Australian Department of Environment, which having seen an earlier version with an entire chapter dedicated to the Reef, requested a redaction of any reference to Australia’s three World Heritage sites, Kakadu National Park, Tasmanian forests and the Great Barrier Reef.
The department’s justification was this was solely a preventative measure against causing panic and confusion, which could adversely affect tourism. Reasoning that the orginal report title, Destinations at Risk: World Heritage and Tourism in a Changing Climate would be misleading, and with the Reef being taken off the ‘at risk’ list the year before, the word ‘risk’ the department argued could confuse people as to the status of the Great Barrier Reef.
Australian Greens Party Deputy Leader and Queensland Senator, Larissa Waters warns “The Government will stop at nothing to cover up the devastating impact its inaction on global warming is having on our World Heritage Areas like the Great Barrier Reef and our magnificent Tassie Wilderness”.
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