ScienceDaily (Aug. 20, 2012) — Life in the world’s oceans faces far greater change and risk of large-scale extinctions than at any previous time in human history, a team of the world’s leading marine scientists has warned. The researchers compared massive sealife extinctions of the past with what is happening now in the seas and oceans. Three of the five largest extinctions of the past 500 million years were associated with global warming and acidification of the oceans — and also loss of oxygen, pollution, habitat loss, and human hunting fishing — all of these trends apply today.
Unless action is taken now, the consequences of our activities are at a high risk of causing, through the combined effects of climate change, over-exploitation, pollution and habitat loss, the next globally significant extinction event in the ocean. The researchers wrote the paper out of their concern that the oceans appear to be on the brink of another major extinction event (Harnik).
The speeds of many negative changes to the ocean are close or equal to the worst-case scenarios. Consequences that already match worst case scenarios include:
- the rate of decrease in Arctic Sea Ice
- accelerated melting of the Greenland and Antarctic ice sheets
- sea level rise
- release of trapped methane from the seabed.
- biodiversity loss
These worst case effects are having the following impacts:
- lowering the distribution and abundance of marine species
- lowering the amount of life in the sea
- increasing harmful algal blooms
- increasing health hazards in the oceans
- causing massive losses of of large, long-lived fish species, resulting in a simplification and destabilization of food webs in marine ecosystems
The magnitude of the cumulative impacts on the ocean is greater than previously understood because the synergistic sum of each negative impact is greater than the a single factor. For example, invasive species, harmful algal blooms, dead zones, biodiversity loss, and coral bleaching are increasing due to:
- overfishing
- physical disturbance
- climate change
- nutrient runoff
- increased temperature and storm intensity
- toxicity of heavy metals increases with acidification
- uptake of plastics by fauna and the pollutants that adhere to plastic
Timelines for action are shrinking. The longer the delay in reducing emissions the higher the annual reduction rate will have to be and the greater the financial cost. Delays will mean increased environmental damage with greater socioeconomic impacts and costs of mitigation and adaptation measures.
The end result will be a marine ecosystem collapse, which obviously will affect us badly, since millions, if not billions of people, depend on the ocean for part or most of their sustenance.
References
Harnik, Paul G., Heike K. Lotze, Sean C. Anderson, Zoe V. Finkel, Seth Finnegan, David R. Lindberg, Lee Hsiang Liow, Rowan Lockwood, Craig R. McClain, Jenny L. McGuire, Aaron O’Dea, John M. Pandolfi, Carl Simpson, Derek P. Tittensor. Extinctions in ancient and modern seas. Trends in Ecology & Evolution, 2012; DOI: 10.1016/j.tree.2012.07.010