Lands & Oceans In Perilous Decline Under Climate Change

Posted on August 23, 2010


At the end of July there was a scientific report which may have been one of the biggest pieces of news in climate change in a decade, in a year, in a season where such news arrives daily.

It was also—in a world where climate disaster is becoming commonplace—among the most depressing news in its implications.  The report, published in the uber-prestigious scientific journal Nature, spoke of a measurable decline of phytoplankton in the world’s oceans under the stress of rising ocean temperatures.

Phytoplankton, just so you know, are microscopic sea plants which produce something like half the organic matter on Earth.  They feed the fishes.  They manufacture oxygen.  They fix carbon and remove carbon dioxide from the atmosphere.

In the grand scheme of things, phytoplankton are as vital as you get.

And if phytoplankton are measurably declining under the pressure of climate change, as the study suggests, then the oceans as a whole are declining.

Boris Worm, marine biologist at Dalhousie University—and one of the authors of the study—is quoted in Climate Progress as saying:

If this holds up, something really serious is underway and has been underway for decades. I’ve been trying to think of a biological change that’s bigger than this and I can’t think of one.

If real, it means that the marine ecosystem today looks very different to what it was a few decades ago and a lot of this change is happening way out in the open, blue ocean where we cannot see it.  I’m concerned about this finding.

Phytoplankton are a critical part of our planetary life support system. They produce half of the oxygen we breathe, draw down surface CO2 and ultimately support all of our fishes.

That phytoplankton story was about a month ago.

A couple of days ago another story came out from NASA talking about the effect of climate change on the world’s crops.

First the ocean, then the land.

Now, one of the climate change deniers’ favourite tactics has been to point out that CO2 is actually good for plants.  Why should we worry, they ask, about a little extra CO2 in the atmosphere?  And, like many effective but misleading arguments, there is some truth in that.  Over the last two decades, and until recently, there has actually been an increase in global agricultural productivity because of carbon dioxide.

Now that increase has reversed itself.  (Everybody expected it to end anyway, because you can’t make a cake when all you have is flour, and you can’t build a plant by stocking up on only one ingredient.)  With worldwide drought offsetting the effects of extended growing seasons and so on, scientists have recently—and much sooner than they expected—measured a net decline in global agricultural production.

Agricultural declines (red) overtake increases (green).

In summary, the oceans are producing less.  The land is producing less.

Under the pressure of climate change, and according to careful scientific measurement, the entire biosphere has become less productive.

What we have seen so far is only a foretaste.  The climate change deniers say we can’t afford to fight climate change.  Can we really afford to do anything else?



Global phytoplankton decline over the past century
Daniel G. Boyce, Marlon R. Lewis and Boris Worm

In the oceans, ubiquitous microscopic phototrophs (phytoplankton) account for approximately half the production of organic matter on Earth. Analyses of satellite-derived phytoplankton concentration (available since 1979) have suggested decadal-scale fluctuations linked to climate forcing, but the length of this record is insufficient to resolve longer-term trends. Here we combine available ocean transparency measurements and in situ chlorophyll observations to estimate the time dependence of phytoplankton biomass at local, regional and global scales since 1899. We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends. These fluctuations are strongly correlated with basin-scale climate indices, whereas long-term declining trends are related to increasing sea surface temperatures. We conclude that global phytoplankton concentration has declined over the past century; this decline will need to be considered in future studies of marine ecosystems, geochemical cycling, ocean circulation and fisheries.

Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009

Maosheng Zhao and Steven W. Running

Terrestrial net primary production (NPP) quantifies the amountof atmospheric carbon fixed by plants and accumulated as biomass.Previous studies have shown that climate constraints were relaxingwith increasing temperature and solar radiation, allowing anupward trend in NPP from 1982 through 1999. The past decade(2000 to 2009) has been the warmest since instrumental measurementsbegan, which could imply continued increases in NPP; however,our estimates suggest a reduction in the global NPP of 0.55petagrams of carbon. Large-scale droughts have reduced regionalNPP, and a drying trend in the Southern Hemisphere has decreasedNPP in that area, counteracting the increased NPP over the NorthernHemisphere. A continued decline in NPP would not only weakenthe terrestrial carbon sink, but it would also intensify futurecompetition between food demand and proposed biofuel production.