It’s Sedimentary: Rethinking the Role of Mud
Sediment starvation is another slowly building crisis, but at least this one has more tractable solutions than Anthropogenic Global Warming (AGW) from Greenhouse Gases (GHG). Check out this piece in Yale Environment 360 that sketches out the problem and the solutions:
Sediment Loss and Restoration
As the article says, Southern Louisiana has lost 2,000 square miles of land and 20% of its wetlands since the 1930’s, when the Army Corps of Engineers set upon the Mississippi River with all the water-taming tools at its disposal. Throughout the world, 57,600 large dams and innumerable small ones are trapping sediment which would otherwise enrich downstream ecosystems.* Robin Grossinger of the San Francisco Estuary Institute likens it to “starving” the ecosystems of “nutrients, minerals, and vitamins [that] these systems need to grow and adapt.”*
Read the article in Yale Environment 360 linked above, for a look at ongoing and potential ways to redistribute trapped sediment, even without necessarily dismantling dams.
Efforts to free up sediments have resulted from a new paradigm among wetlands scientists, most of whom 10 or 20 years ago “viewed sediment as a negative’ and now see it as a resource,” according to marine ecologist Richard Ambrose. (Why they ever saw it as a net negative begs for an explanation, but I’ll take Richard Ambrose’s word on it.)
Sediment Entrapment and Greenhouse Gas Excesses: Not Parallel Problems
Unfortunately, the promising measures to redistribute sediment don’t translate well to efforts either to cut production of carbon dioxide or to pull it out of the air (or smokestack) and bury it.
To begin with, how do you persuade people to take greenhouse gases seriously when you can’t even see them? If CO2 were emitted in red clouds from automobile tailpipes and power plant chimneys, it would definitely get more attention. It’s the “out of sight, out of mind” factor, and few of us are immune to it.
Whereas sediment, while mostly out of sight, is a tangible and visible material once you go underwater, and fairly easily measured—you can do a lot with little more than a steel pole. Compelling, visible evidence of the lack of it can be seen in the losses of land and wetlands in Louisiana.
Another difficulty is that GHG emissions disperse quickly. Even if CO2 came out of automobile tailpipes in red clouds, you couldn’t capture it the way a dredge can rake up sediment. It would disperse into a less and less noticeable haze. Sediment’s concentration facilitates moving it from places it shouldn’t be to places it should be, whether by vehicle transport or the special portals in China’s Xiaolangdi Dam on the Yellow River.
Finally there’s the matter of scale: CO2 is an immense global problem; sedimentation has less overall impact and can be geographically targeted
Solutions to AGW require scientific sophistication and/or a lot of money. The measures discussed in Yale Environment 360 for measuring, rescuing, and redistributing sediment are relatively low-tech. Not so are solutions to the carbon emissions problem.
Let’s frame the carbon emissions problem by recognizing that worldwide demand for energy is not going to drop in the next 30-50 years, and will probably increase. That’s because progress in efficiency and conservation can barely keep pace with rises in population and standard of living, especially in China, India, and Africa.
Assuming constant or increased demand, there are three broad approaches to the AGW problem:
(1) advance no-carbon energy production of electric power generation, and power for vehicles, at a much faster pace than we are now seeing (I’ve left out the issue of heating fuel in the form of natural gas, petroleum, and wood, another problem we don’t hear much about). Downside: it’s not happening.
(2) adapt the environment in the form of massive infrastructure projects, in addition to large-scale transformation of agriculture. Downside: poorer countries, where land is more vulnerable to climate change than in developed countries, cannot afford it on their own.
(3) geoengineering a way to cool the Earth even as CO2 rises or fails to drop. Downsides: the good old whammies of unintended consequences.
Any of these three present tough technical challenges, although some scientists believe that the low-tech injection of aerosols into the stratosphere might do the cooling trick—since volcanoes have already demonstrated the effectiveness of it. Needless to say, such a project is yet another experiment in modifying the environment with multiple consequences, to include unknown ones as well as known bad ones. ** But, not to be too fatalistic, geoengineering of one kind or another is practically inevitable, the way we’re going.
* All stats and quotes here are drawn from the Yale Environment 360 paper at the linked website.
** For upsides and downsides of the sulfate aerosol idea, see: