Sparks

Good news for climate

 By RP Siegel

It’s hard to find much good news these days when it comes to climate change. The more we learn, the more it seems that previous assessments were too optimistic, as new effects that hadn’t been considered before, are being discovered. Many of these will serve to further stress our planet’s beleaguered climate…

(cover photo by UCL Mathematical & Physical Sciences CC 2.0)

While today’s news is not a game-changer, it does show that there are some natural forces on the planet, that we never knew about, that are, and long have been acting towards equilibrium. That is to say, they are working with us in our fight to ward off the worst consequences of climate change.
Ben Houlton is the director of the John Muir Institute of the Environment at the University of California, Davis. His expertise is in ecosystem biogeochemistry, which looks at the interface between living systems and geology. For years, Houlton has studied the nitrogen cycle. Nitrogen is a building block for DNA, making it a crucial element for all living things. While nitrogen is extremely plentiful, it constitutes close to 80 percent of air, most of it is in a form that living organisms can’t use because it is highly inert. In fact, the amount of nitrogen available in a given area, is often the limiting factor in the growth of plants. This is the rationale behind the development and use of chemical fertilizers, which provide supplemental quantities of nitrogen, along with phosphorus and potassium.
We know that the presence of carbon dioxide in the air can help boost the growth of some plants (another negative feedback loop that works in our favor), which can then remove CO2 from the atmosphere, storing it in their leaves, stems, bark, etc., as they grow. But the amount they can grow, as we said earlier, it can be limited by the amount of available nitrogen.

nitrogen-cycle-rock-weathering
Tafoni, a class of cavernous rock weathering structures, which likely develop in large part by chemical and physical salt weathering processes (Dawn Endico, Wikimedia)

The discovery

What Houlton discovered, using techniques like isotopic fingerprinting to trace nitrogen molecules as they make their way through the environment, was that the amount of nitrogen contained in bedrock is much higher than previously thought. We now know that much as 26 percent of all the nitrogen on the planet resides in the ground. It’s the weathering of the rocks that breaks the nitrogen free. What this means is more total nitrogen available for plant growth, than scientists had thought.
“Prior to our work,” said Houlton, “it was assumed that the nitrogen that enters the ecosystems on Earth come from the atmosphere through a couple of different pathways.” Geologists have known since the ’70s that there was a great deal of nitrogen stored in rocks, but they weren’t particularly interested in that fact. Houlton “drew a bridge between that discovery, and soils and plants.”
While the rocks may have been deep underground when they stored the nitrogen they gradually work their way to the surface through a process called tectonic uplift, which eventually brings them close to the surface where they are exposed to the elements and available to the roots of plants. Houlton went on to study this and verify that it is true, “in a way that is meaningful to biology.”
“The Implication,” says Houlton, “is that a lot of models have suggested that as the climate continues to change, the terrestrial ecosystems will not be able to continue to absorb our CO2 emissions. Right now, about 25 percent of our CO2 emissions are taken up by living plants and the soil.” But many of these models predict that this process will be eventually be curtailed by a lack of available nitrogen. “What we’re saying is that could be true still, but there’s a lot more nitrogen available to ecosystems than we thought before. This means they could store out carbon pollution for a longer time than we had previously thought.”

To save the planet

Houlton claims that the role of rocks in the survival of living systems has been greatly underestimated. He went so far as to say, “without rock weathering the entire Earth system, would cease.”

nitrogen-cycle-rock-weathering
Rock colonised and broken down by vegetation growing in the widening joints of the rock (Christine Christie)

“Over geologic time scales (millions of years), rock weathering is what controls the Earth’s climate.” This, explains Houlton, is because the rate of rock weathering increases with temperature. As the rocks weather, they store CO2. When it’s cooler, they store less. So this feedback effect acts to regulate the planet’s temperature.
The bottom line is that rock weathering is an integral of part of the living planet. This is particularly pertinent today. Rock weathering alone is responsible for.
“Not only do we need to think about this on million year times scales, we also need to think about it on decade to century time scales, because the nutrients which are coming from the rocks, also participate in the carbon cycle, by feeding life on the planet. The current modeling suggests that weathering by itself is about 0.3 GT of carbon removal per year. But also have to consider that they release this nitrogen which then allows the plants to absorb more of our CO2. So we really have to start tracing a rock’s full journey, through the carbon cycle to better understand how we can predict climate change this century.”

READ MORE: Removing carbon from the air by Amanda Saint

about the author
RP Siegel
Skilled writer. Technology, sustainability, engineering, energy, renewables, solar, wind, poverty, water, food. Studied both English Lit.and Engineering at university level. Inventor.