Ocean predators can help reset our planet’s thermostat


Peter Macreadie, University of Technology Sydney; Euan Ritchie, Deakin University; Graeme Hays, Deakin University; Rod Connolly, Griffith University, and Trisha B Atwood, Utah State University

If you knew that there was zero percent chance of being eaten by a shark, would you swim more often? Rhetorical questions aside, the fear of being eaten has a profound influence on other animals too, and on the way they use marine environments.

Turtles, for example, fear being eaten by sharks and this restricts the movement and behaviour of entire populations. But when the fear of being eaten dissipates, we see that turtles eat more, breed more, and go wherever they please.

It might sound like turtle paradise, but in an article published today in Nature Climate Change we show that loss of ocean predators can have serious, cascading effects on oceanic carbon storage and, by extension, climate change.

Cascading effects

For a long time we’ve known that changes to the structure of food webs – particularly due to loss of top predators – can alter ecosystem function. This happens most notably in situations where loss of predators at the top of the food chain releases organisms lower in the food chain from top-down regulatory control. For instance, the loss of a predator may allow numbers of its prey to increase, which may eat more of their prey, and so on. This is known as “trophic downgrading”.

With the loss of some 90% of the ocean’s top predators, trophic downgrading has become all too common. This upsets ecosystems, but in our article we also report its effects on the capacity of the oceans to trap and store carbon.

This can occur in multiple ecosystems, with the most striking examples in the coastal zone. This is where the majority of the ocean’s carbon is stored, within seagrass, saltmarsh and mangrove ecosystems – commonly known as “blue carbon” ecosystems.

Blue carbon ecosystems capture and store carbon 40 times faster than tropical rainforests (such as the Amazon) and can store the carbon for thousands of years. This makes them one of the most effective carbon sinks on the planet. Despite occupying less that 1% of the sea floor, it is estimated that coastal blue carbon ecosystems sequester more than half the ocean’s carbon.

The carbon that blue carbon ecosystems store is bound within the bodies of plants and within the ground. When predators such as sharks and other large fish are removed from blue carbon ecosystems, resulting increases in plant-eating organisms can destroy the capacity of blue carbon habitats to sequester carbon.

For example, in seagrass meadows of Bermuda and Indonesia, less predation on herbivores has resulted in spectacular losses of vegetation, with removal of 90–100% of the above-ground vegetation.

Stop killing predators

Such losses of vegetation can also destabilise carbon that has been buried and accumulated over millions of years. For example, a 1.5-square-kilometre die-off of saltmarsh in Cape Cod, Massachusetts, caused by recreational overharvesting of predatory fish and crabs, freed around 248,000 tonnes of below-ground carbon.

If only 1% of the global area of blue carbon ecosystems were affected by trophic cascades as in the latter example, this could result in around 460 million tonnes of CO2 being released annually, which is equivalent to the annual CO2 emissions of around 97 million cars, or just a bit less than Australia’s current annual greenhouse gas emissions.

So what can be done? Stronger conservation efforts and modification of fishing regulations can help restore marine predator populations, and thereby help maintain the important indirect role that predators play in climate change mitigation.

It’s about restoring balance so that we have, for example, healthy and natural numbers of both sea turtles and sharks. Policy and management need to reflect this important realisation as a matter of urgency.

More than 100 million sharks may be killed in fisheries each year, but if we can grant these predators great protection they may just help to save us in return.

The Conversation

Peter Macreadie, Senior lecturer & ARC DECRA Fellow, Deakin University and Senior lecturer & ARC DECRA Fellow, University of Technology Sydney; Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University; Graeme Hays, Professor of Marine Science, Deakin University; Rod Connolly, Professor in Marine Science, Griffith University, and Trisha B Atwood, Assistant Professor of aquatic ecology, Utah State University

This article was originally published on The Conversation. Read the original article.

Article: Solar System – New Planet?


The following link is to an article reporting on the possible discovery of a new planet in the solar system.

For more visit:
http://news.nationalgeographic.com/news/2012/05/120511-new-planet-solar-system-kuiper-belt-space-science/

Earth Hour 2012: Tonight


The link below is to an article on Earth Hour 2012, which is being held tonight. The article below includes a history of the event, which is now a global movement for ‘change.’ However, just how much change is brought about by Earth Hour is still a matter of debate. There seems to be more of an emphasis on going beyond the hour this time round, which is a far better way of drawing awareness to the need of green energy for the future and the major issue of climate change that is facing the planet. If the event is to is bring lasting change, we need to move beyond the hour as just a fun thing to do and actually bring about change to the way we live our lives the world over. There is a long way to go, as can be seen with the great difficulty of reaching any useful agreements on CO2 emission reductions and the like. Hopefully awareness can bring about real change through this event.

For more visit:
http://www.kleenexmums.com.au/sustainability/earth-hour/the-hour-of-no-power/

Earth Day (April 22): Picnic for the Planet


April 22 is Earth Day and to celebrate Earth Day, The Nature Conservancy is asking people to have a Picnic for the Planet. The idea is to raise awareness by going on a picnic to some outdoor location with a group of friends and to celebrate the planet we live on – or to give thanks for it.

For more visit:
http://earthday.nature.org/

Plants Under Threat Around the World


When we think of species threatened with extinction, we tend to think of animal, bird and fish species – not necessarily plant species. Never before has so many of the planet’s plant species been threatened with extinction in the wild. One web site concerned with bringing awareness of the plight of the planet’s plant species is Plantlife. Visit the site below to find out more about the threat to our planet’s plantlife.

http://www.plantlife.org.uk/

The site deals primarily with the situation in Great Britain, but there is also an international side to the site. Visit the URL below to visit that part of the site.

http://www.plantlife.org.uk/international

Copenhagen Summit Fails to Deliver


In news that has delighted the ears of climate change sceptics the world over, the Copenhagen summit on climate change has failed to deliver anything of real value that will actually make a difference. It is truly disappointing that even in the face of a massive environmental disaster that will affect the entire planet, global leaders have failed to lead and work together in finding solutions to the major issues we face over the coming decades and century.

Newspapers in Australia have reported the failure of the summit and are reporting on the leader of the opposition gloating over the failure of the summit. His solution is to ignore the real issue and hope that the Australian people prove to be as oblivious to climate change as the coalition he leads.

Typically, the usual anti-Kevin Rudd biased journalists and climate change sceptics of the newspaper (The Sunday Telegraph) I read this morning, were also quick to pour further scorn on the Prime Minister and the problem of climate change itself (which they deny). One particular vocal climate change sceptic in the Sunday Telegraph has very little credibility with me and I find his obsessive anti-Rudd tirades more than a little tiring. This self-opinionated buffoon is little more than an embarrassment for both the Sunday Telegraph and the Daily Telegraph for which he also writes. His columns are becoming more of a personal vendetta against Kevin Rudd than anything resembling real journalism.

I’ll be finding a better way to become acquainted with the daily news than continuing to read the biased diatribes that continue to be put forward by these papers in future. I’ll also be hoping that our leaders can overcome the various preoccupations each have with self-interest (whether it be personal or national) in order to reach a real workable agreement on dealing with the growing threat of climate change