“The huge carbon sinks that are global forests and soils have served as a planetary pressure valve for our own burgeoning emissions over the last century. If we fail to cut emissions deep and fast then these vast sinks could falter and increasingly switch from carbon-absorbing friend to big-emitting foe.” Dave Reay, Professor of Carbon Management and Education at the University of Edinburgh
Scientists have concluded that human greenhouse emissions have had an impact on drought since 1900. These droughts have had a serious negative influence on soils ability to store carbon — turning it from a carbon sink to a carbon source according to a study published in Nature on January 23, 2019. Soil is one of two terrestrial carbon sinks, the other being plants ability to sequester carbon can only last so long before the plant reaches a saturation point. At that time, plants will become a carbon source bringing the planet even closer to the tipping point.
This diary is lengthy, so I will keep my commentary brief. Suffice it to say that things are accelerating and falling apart on the climate front. Unfortunately, we have the grim reaper occupying the White House, so don’t expect a fix for our dilemma anytime soon.
Kashmira Gander writes in Newsweek about the grim findings regarding the loss of soil and forests from a friend of climate to an enemy.
Currently, the terrestrial biosphere—which is made up of the Earth’s vegetation and land—soaks up around 25 percent of carbon dioxide emissions caused by humans. However, moisture levels in the biosphere impact the amount it can absorb. As we experience more periods of extreme dryness and wetness, these natural sinks are being put at risks, found the authors of a study published in the journal Nature.
In turn, the subsequent build-up of carbon dioxide could cause global warming to speed up.
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"This is a big deal! If soil moisture continues to reduce NBP (net biome productivity) at the current rate, and the rate of carbon uptake by the land starts to decrease by the middle of this century—as we found in the models—we could potentially see a large increase in the concentration of atmospheric CO2 and a corresponding rise in the effects of global warming and climate change."
She told Newsweek the tipping point for maximum carbon absorption could be reached as soon as 2060. Also, she was shocked to find "just how large the effects of soil moisture are."
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Dave Reay, Professor of Carbon Management and Education at the U.K’s University of Edinburgh told Newsweek: “This study further confirms what we have long feared. Climate change impacts like drought are already eroding the natural sinks for carbon around the world. Each forest transformed to dry savannah or peat land desiccated by drought means less carbon is locked up and more is left in the atmosphere—enhancing warming yet further.”
Sarah DeWeerdt has an interesting piece in Anthropocene Magazine on how we may have been overestimating the ability of plants to absorb carbon.
Plants take in carbon dioxide and release water through small pores in their leaves called stomata. So, plants must often make a tradeoff between carbon gain and water loss. Boucher and his team found that boreal white cedars’ intrinsic water use efficiency – the amount of carbon assimilated per unit of water lost – has increased a whopping 59% since 1850. This increased water use efficiency should make the trees more resistant to drought. The findings suggest that mature trees, even ancient ones, have the capacity to acclimate to increased carbon dioxide levels.
However, the researchers also found that the trees are not growing any faster than they did in the preindustrial period. That suggests that even though increased carbon dioxide levels may stimulate photosynthesis, this does not necessarily translate into increased carbon storage in above-ground biomass. “Carbon fertilization is ultimately much more complex than what vegetation models usually assume,” Boucher says.
Both papers also suggest that plants’ capacity to sop up excess carbon dioxide from the atmosphere is finite. After all, trees evolved for thousands of generations in an atmosphere containing less than 290 parts per million of carbon dioxide; current atmospheric carbon dioxide is at 405 parts per million. “There is a point at which the photosynthesis apparatus saturates,” says Boucher, comparing the situation to a person fed 6 meals a day rather than the usual 3. “The photosynthetic system just can’t take it anymore.”
“It has long been predicted by the World’s scientific community that there would come a time when our planetary resources would become depleted, waste arisings and pollution of the land, air, and water would seriously affect the environment we live in and at the same time, human numbers would become unsustainable. We have now reached this point, global warming threatens to tip us over into disaster.” Toby Clark , Tipping Point
Roger Harribin writes on the BBC website about the dire condition of our soils.
About 3.2 billion people worldwide are suffering from degraded soils, said IPBES chairman Prof Sir Bob Watson.
"That's almost half of the world population. There’s no question we are degrading soils all over the world. We are losing from the soil the organic carbon and this undermines agricultural productivity and contributes to climate change. We absolutely have to restore the degraded soil we’ve got."
Prof Watson previously led the Inter-governmental Panel on Climate Change (IPCC).
"Governments have focused on climate change far more than they have focused on loss of biodiversity or land degradation. All three are equally important to human wellbeing."
Soil expert Prof Jane Rickson from Cranfield University, UK, added: "The thin layer of soil covering the Earth's surface represents the difference between survival and extinction for most terrestrial life.
Gabriel Popkin writes in Quanta Magazine on how plants move water and CO2 between the soil and plants that can influence weather across continents.
When Abigail Swann started her career in the mid-2000s, she was one of just a handful of scientists exploring a potentially radical notion: that the green plants living on Earth’s surface could have a major influence on the planet’s climate. For decades, most atmospheric scientists had focused their weather and climate models on wind, rain and other physical phenomena.
But with powerful computer models that can simulate how plants move water, carbon dioxide and other chemicals between ground and air, Swann has found that vegetation can control weather patterns across huge distances. The destruction or expansion of forests on one continent might boost rainfall or cause a drought halfway around the world.
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Atmospheric scientists — and everyone else — could be excused for thinking of a stoically standing tree or a gently undulating wheat field as doing little more than passively accepting sunlight, wind and rain. But plants are actually powerful change agents on the planet’s surface. They pump water from the ground through their tissues to the air, and they move carbon in the opposite direction, from air to tissue to ground. All the while, leaves split water, harvest and manipulate solar energy, and stitch together hydrogen, oxygen and carbon to produce sugars and starches — the sources of virtually all food for Earth’s life.
The key features of this molecular wizardry are pores, called stomata, in plant leaves. A single leaf can contain more than 1 million of these specialized structures. Stomata are essentially microscopic mouths that simultaneously take in carbon dioxide from the air and let out water. As Swann notes, the gas exchange from each stoma — and indeed from each leaf — is, on its own, tiny. But with billions of stomata acting in concert, a single tree can evaporate hundreds of liters of water per day — enough to fill several bathtubs. The world’s major forests, which contain hundreds of billions of trees, can move water on almost inconceivably large scales. Antonio Nobre, a climate scientist at Brazil’s National Institute for Space Research, has estimated, for example, that the Amazon rainforest discharges around 20 trillion liters of water per day — roughly 17 percent more than even the mighty Amazon River.
We can’t dither any more, as the tipping point to catastrophe is near. Trump must lose the presidency along with his enablers in the GOP before we are able to seriously address this issue. Let’s hope out Democratic nominee is not an incrementalist.
Thanks for reading. Hug your loved ones and vote green.