Root Zone Wetness

“We have to be aware that climate change and biodiversity loss are stress factors for ecosystems, for humans, for animals, and for the microbiome. Our research shows that if the different axes of the disease pyramid are destabilized, new infectious diseases can be expected, including for humans.” Dirk Schmeller, Université de Toulouse

Forests, like the ocean, help keep our climate safe and stable by absorbing carbon dioxide through photosynthesis. The process shows how the forest uses solar energy from the sun and CO2 to feed themselves and to grow. The CO2 gets stored below the ground and above the ground like leaves and needles.

A healthy forest will absorb CO2 and release oxygen into the atmosphere. Terrestrial plants pull  30% of our fossil fuel emissions, according to Monga Bay. They note that “for forests to be good carbon-removal investments, they need to be relatively permanent, meaning that the plants and soil in a forest will absorb carbon and keep it locked away for decades or centuries. What climate change does is exacerbate many of the threats to forest permanence.”

Most of the earth's vast forests teeming with biodiversity are only fragmented now in many parts of the world. Reforestation is seen as a “low cost, high impact solution to climate change.” by many governments. As a result, many nations have begun massive tree-planting campaigns as a carbon drawdown.

According to the BBC, scientists have warned these same campaigns planting forests may be a bad idea by eliminating biodiversity and releasing more carbon.

While it was intended not to apply to existing forests, lax enforcement and budgetary limitations meant that some landowners simply replaced native forests with more profitable new tree plantations.

Their study found the subsidy scheme expanded the area covered by trees but decreased the area of native forest.

They point to the fact that in the Bonn Challenge nearly 80% of the commitments made to date involve planting monoculture plantations or a limited mix of trees that produce specific products such as fruit or rubber.

The authors of this new study have looked closely at the financial incentives given to private landowners to plant trees.

These payments are seen as a key element of increasing the number of trees significantly.


In their article, they provide a case study from Chili.

The law subsidised 75% of the costs of planting new forests.

While it was intended not to apply to existing forests, lax enforcement and budgetary limitations meant that some landowners simply replaced native forests with more profitable new tree plantations.

Their study found the subsidy scheme expanded the area covered by trees, but decreased the area of native forest.

The authors point out that since Chile's native forests are rich in biodiversity and store large amounts of carbon, the subsidy scheme failed to increase the carbon stores and accelerated biodiversity loss.

“If policies to incentivise tree plantations are poorly designed or poorly enforced, there is a high risk of not only wasting public money but also releasing more carbon and losing biodiversity,” said co-author Prof Eric Lambin, from Stanford University.

NASA writes on the loss of groundwater in Europe. 

The maps on this page show shallow groundwater storage (above) and root zone soil moisture (below) in Europe as of June 22, 2020, as measured by the Gravity Recovery and Climate Experiment Follow On (GRACE-FO) satellites. The colors depict the wetness percentile; that is, how the levels of groundwater and soil moisture compare to long-term records for the month. Blue areas have more abundant water than usual, and orange and red areas have less. The darkest reds represent dry conditions that should occur only 2 percent of the time (about once every 50 years).

Root Zone Wetness
Root Zone Wetness Percentile

Groundwater Wetness Percentile
Groundwater Wetness Percentile

Note the differences between the groundwater and root zone moisture maps. Monitoring root zone moisture is essential for managing agriculture because it is the water naturally available for growing crops. Soil moisture at Earth’ surface and in the root zone can fluctuate significantly over short periods of time; it can be quickly replenished by rainfall, but also can evaporate rapidly during heat waves and dry spells. In fact, recent rains in parts of Europe have significantly reduced surface moisture deficits.

Groundwater is a deeper resource for crop irrigation and drinking water, and it also sustains streams during dry periods. Unlike surface and root zone moisture, groundwater takes months to rebound, as it has to be slowly and steadily replenished by surface moisture that seeps down through soil and rock to the water table. Because much of Europe experienced drought in the summers of 2018 and 2019, and saw little snow in the winter of 2019-20, much of the continent began this year with a significant deficit.

“In recent years, Central Europe has experienced a series of droughts caused by exceptionally stable weather patterns and high temperatures that can both be linked to climate change,” said Wolfgang Wagner, a remote sensing scientist at Technische Universität Wien. “The fact that some regions have experienced drought conditions in several consecutive years has already caused significant damage to forests (due to bark beetle infestation) and declines in groundwater levels.”



The University of Würzburg in a presser from the Julius-von-Sachs-Institute for Biosciences notes how climate extremes will force changes in forests.

“At such temperatures, our Central European vegetation reaches its limits,” says the JMU professor. Together with other researchers from Germany and Switzerland, the plant ecologist was able to confirm with physiological measurements: When it is too hot, the tree simply loses too much water via its surface. As a result, the negative tension in the wood's conducting tissue becomes too steep, which ultimately leads to hydraulic failure interrupting the water transport.

Already during the course of the summer, severe drought-related stress symptoms were observed in most ecologically and economically important tree species, including widespread leaf discoloration and premature lead shedding.

Moreover, unexpectedly strong drought-legacy effects were detected in 2019: many broad-leaved trees did not unfold their leaves – they had died. Others that survived the 2018 event where not able to withstand the following drought in 2019, or became increasingly susceptible to infestation with bark beetles or fungi.

“Spruce was most severely affected, mainly because this mountainous species has been planted outside its natural habitat in Central Europe,” explains Schuldt. “Unexpected was, however, the extent to which beech trees were affected. Here in Northern Bavaria, I have seen several stands with complete dieback, especially on sites with shallow soil”. Until this event, beech has been considered as “future tree species”, even though its drought tolerance has been controversially discussed since the hot drought in 2003.

This year’s climatic condition in spring again started too warm and too dry. “Now in June 2020 we have fortunately received high amounts of rainfall,” the Würzburg professor is pleased to report. This has mitigated the situation, but the water deficit in the deeper soil layers has certainly not been recharged. Therefore, he assumes that affected trees will continue to die-off in the coming years due to legacy effects.


Bob Berwyn of Inside Climate News writes an excellent review of new studies that show drought and heat killing most trees that are alive today.

The study, published April 17 in the journal Science, reviewed the last 10 years of research on tree mortality, concluding that forests are in big trouble if global warming continues at the present pace. Most trees alive today won't be able to survive in the climate expected in 40 years, Brodribb said. The negative impacts of warming and drying are already outpacing the fertilization benefits of increased carbon dioxide.

Trees and forests can be compared with corals and reefs, he said. Both are slow-growing and long-lived systems that can't easily move or adapt in a short time to rapid warming and both have relatively inflexible damage thresholds. For corals, a global tipping point was reached from 2014 to 2016. In record-warm oceans, reefs around the world bleached and died.

The detailed new information and modeling on how water stress kills trees suggest there is a similar drought threshold for tree mortality, beyond which forests could also perish on a global scale, he said.

“Nobody predicted the coral bleaching scenario. If a similar thing evolves with forests, that is pretty catastrophic,” he said. “We're at a point where we can see the process, we can predict it. It's time to start making some noise about it. We can't afford to sit on our hands.”


At the current pace of warming, much of the world will be inhospitable to forests as we know them within decades. The extinction of some tree species by direct or indirect action of drought and high temperatures is certain. And some recent research suggests that, in 40 years, none of the trees alive today will be able to survive the projected climate, Brodribb said.

“That's one of the potential scenarios, and we need to know if that's right. We have to establish the consequences of rising temperatures unequivocally for policy makers,” he said.

The stakes are high, since trees are the foundation for terrestrial biodiversity and because they capture and store about one-third of human-caused CO2 emissions within their dense wood frames. A global loss of forests could lead to a surge in heat-trapping carbon dioxide, causing more warming, and would also eliminate habitat for countless other animals, plants and fungi, with a rippling effect that reaches humans.

In just four decades, Ebola has wiped out one third of the world’s chimp and gorilla populations. If it continues, the results will be devastating.
In just four decades, Ebola has wiped out one-third of the world’s chimp and gorilla populations. If it continues, the results will be devastating. Daily Beast

The Edinburgh Reporter published an article titled “How forest loss has changed biodiversity over the last 150 years” that you might find interesting.

The Earth’s forests have been changing ever since the first tree took root. For 360 million years, trees have grown and been felled through a dynamic mix of hurricanes, fires and natural regeneration. But with the dawn of the 17th century, humans began replacing large swathes of forest with farms and cities.

The global pace of deforestation has slowed in the 21st century, but forests are still disappearing – albeit at different rates in different parts of the world. Boreal forests, which grow in the far north of the world and across vast areas of Canada and Russia, are expanding further north as the climate warms, turning tundra into new woodland. Many temperate forests, like those in Europe, saw their greatest destruction centuries ago. But in the tropics, forest loss is accelerating in previously pristine wilderness.


Changes in biodiversity didn’t always immediately follow forest loss. We discovered that the pace at which forest loss altered biodiversity differed among short-lived species, such as light-loving plants like St John’s wort, and longer-lived species like red-tailed hawk. The longer the lifespan of a species, the longer it took for the effects of forest loss to register.

Sometimes the effects carried across generations. Red-tailed hawks may manage to raise their young alongside deforestation, but these offspring may struggle to prosper in the shrinking habitat, and ultimately fail to produce young of their own. If resources are scarce, species with longer lifetimes could persist but not reproduce for decades. That’s how the impact of forest loss on such species might only appear decades after the first wave of deforestation.


Currently, the most biodiverse regions of the planet are located near the equator. Countries such as Brazil, Ecuador, the Philippines, the Democratic Republic of Congo and Papua New Guinea, with stunning levels of biodiversity.


The study examined the biodiversity of the planet before and after the Permian-Triassic extinction. Areas near the equator grew to be far too hot, and the variety of life dropped significantly. Even the seas were empty. Unlike today, the most biodiverse areas of the planet shifted north and south, closer to mid-latitudes.

Human-caused climate change will warm the planet, but not to the levels seen during the Permian extinction. Still, it’s important to understand what the consequences may be.

“In the face of a rapidly warming planet, this window into our past could offer a glimpse into the future of those regions and the very real risk to the species that live there if we do not act to curb our carbon emissions and limit global warming,” says study lead Bethany Allen.

Medical News Today writes on how climate change will affect the microbiome and lead to new diseases.


Microbiome may mediate link between climate change and new diseases

The COVID-19 pandemic has brought the threat of infectious disease to the fore. At the time of writing, there have been more than 9 million recorded cases of the disease worldwide.

Infectious diseases, particularly those crossing species boundaries (zoonoses), are rising as a result of human activities. This increase is partly due to climate change, which is encouraging some pathogen-carrying species to move outside their current habitat range.

For example, the tiger mosquito, which transmits the viral disease Chikungunya, is currently expanding its geographic range across Europe and the Americas, putting millions of people at risk.

A paper that Trends in Parasitology recently published includes a synthesis of research into infectious diseases in humans and wildlife. It presents a new model of infectious disease dynamics that takes account of the role of the microbiome — the “good” bacteria that live on and inside us.

The scientists behind the work suggest that environmental changes, including climate change, could destabilize this model and lead to new infectious diseases arising from changes in the microbiome of animals.


In disease ecology, scientists traditionally use a “disease triangle” to demonstrate the roles of the host, pathogen, and environment in the spread of disease.

The authors of the new study, who represent institutions in France, Germany, and the United States, suggest that this concept gives an “oversimplified” view of the dynamics of infectious diseases. They have, therefore, broadened the concept to include the microbiome.

The microbiome describes the communities of microorganisms, including bacteria, viruses, and fungi, in a particular context. In an animal context, microbial communities live on and inside the host and perform important roles, including protecting against pathogens and helping break down food.

Research has shown that microbial communities are important for the health of ecosystems, wildlife, and people. The human gut alone is home to up to 1,000 different species of bacteria, which researchers have shown to be important in many aspects of health.

  • June 30, 2020
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