The water's warm...

Tigers, rainforests, polar bears - when considering the big focuses of international conservation, I feel that marine ecosystems often get a bit left out. Since ocean biodiversity and its reaction to climate change is something I admit to knowing very little about, I thought I’d take the chance this week to delve into a different aspect of biodiversity loss.

Marine ecosystems are typically affected by anthropogenic use in more indirect ways than terrestrial systems. This year has seen the reports of increasing bleaching of coral reef ecosystems, with particularly high-profile reports that climate change had induced bleaching in coral of the Great Barrier Reef to an extent that many scientists were declaring it beyond help. Coral bleaching is no new thing – but for many ocean areas the phenomena is reaching a critical point.

What is coral bleaching? 

Stressed coral (credit: wikipedia)

Coral reefs are highly diverse, in fact containing the highest concentration of biodiversity of all marine habitats. The coral itself is host to algae called ‘zooxanthellae’, the coral’s main source of energy. Increased ocean temperatures or pollution causes the algae to leave the coral’s tissue. The result of this is coral left without its food source and more vulnerable to disease. The lack of algae also means it turns very pale or white (“bleached”). This means that coral reef ecosystems are particularly vulnerable to climate induced warming. Their death can lead to the collapse of the whole ecosystem with the many species dependent on the habitat for nutrients or shelter being thrown into peril.

Research has for several years now suggested that current warming scenarios will lead to long-term degradation of coral reefs, but the news that 25% of the Great Barrier Reef’s coral has died following a mass bleaching event shocked the world in the way that only a catastrophe in a charismatic habitat could.

Despite this, there is hope in the ability of these ecosystems to recover. A word associated with coral reefs in many publications is ‘resilience’ – the reefs themselves embody this key anthropocenic buzz word. According to Hughes et al the variability in gene flow in coral species implies a differentiating ability to result to climate change, and they suggest that rather than see a destruction of coral reefs in the future, we may well instead see a change in their structure and species composition.  Reef recovery is helped greatly by interconnection of reef ecosystems (benefits of habitat connectivity again showing up), but there is evidence that long-distance dispersal of species could also play a significant role. Crucially, coral reefs also present a case where local conservation efforts can play a large role, with the development of no-take areas already proving to help preserve fish stocks and reduce some pressure on the ecosystem under stress.

When looking into coral reef ecosystems I wasn’t expecting to come across geo-engineering solutions, but it turns out there have been suggestions of such measures  – like a ‘shade cloth’ to protect reefs from heat stress (think a giant sun umbrella), and even more drastic measures such as genetic engineering to ‘assist evolution’ of coral species.  

The topics in this blog – biodiversity loss, extinction, climate change – can seem a bit negative and depressing at times, so it’s nice to see efforts to turn the cynical news on coral reefs into something more motivating that could get people past the 'we're all doomed' state and onto practical action that can be taken to aid conservation. Whilst I am sceptical on the potential of geoengineering solutions, the sense I get from research and news media a few months on is that whilst prospects for coral reefs are dire if climate change continues at its current rate, there is potential to conserve these ecosystems if we act appropriately and allow them to recover through removing the stresses we place upon them.