Tropical Response to CO2
A study appeared in Trends in Ecology & Evolution in the year 2000 that looked at the response of tropical forests to the increasing amounts of atmospheric carbon dioxide. The authors, Yadvinder Malhi and John Grace, were with the Institute of Ecology and Resource Management, University of Edinburgh, Scotland. Their report, appearing in the Perspectives section of the journal, began by discussing what they presumed to be the inexorable future rise of atmospheric CO2 concentrations due to fossil fuel burning and land clearing, and the implications of this increase to global climate change. They then qualify their statements by saying: “However, these changes are meshed within an immense natural global carbon cycle that is still poorly understood and that will almost certainly provide new surprises.” [See: Mahli, Yadvinder, and John Grace. “Tropical forests and atmospheric carbon dioxide.” Trends in Ecology & Evolution Vol 15, No. 8 (2000): 332-337.]
The two things these authors emphasize should be kept in mind before continuing: the immensity of the natural carbon cycle relative to the contributions of humans, and the fact that this immense natural phenomenon, which, in the authors’ words “is still poorly understood” is central to the question of climatic consequences.
If the authors are right, that the immense natural carbon cycle is “still poorly understood,” how is it possible to be so absolutely certain of outcomes that we can declare the debate over and the science settled with respect to the matter of climate change?
[pullquote]If the authors are right, that the immense natural carbon cycle is “still poorly understood,” how is it possible to be so absolutely certain of outcomes that we can declare the debate over and the science settled with respect to the matter of climate change?[/pullquote]
Mahli and Grace refer to a synopsis, published in the journal Tellus a year earlier, entitled Current perspectives on the terrestrial carbon cycle, by Jon Lloyd. They discuss some of the findings presented in Lloyds’ synopsis:
“A recent review of experimental studies growing trees in open-top chambers indicates that a 300 ppm increase in atmospheric CO2 concentration stimulates photosynthesis by 60%, the growth of young trees by 73% and wood growth per unit leaf area by 27%. It seems probable that there will be a similar response in natural forest ecosystems.”
In the context of the notable findings of Jon Lloyd, Mahli and Grace proceed to discuss the implications for the tropics:
“Because of their intrinsic high productivity, tropical forests are a prime candidate for such a C fertilization response, the crucial question has been to what extent such a response might be limited by nutrient availability, in particular by low nitrogen or low phosphorus.” However, as they point out, studies referenced by Lloyd have shown that plants might “increase their nutrient acquisition process by investing in mycorrhizal colonization, and by mineralizing nutrient reserves in the soil by the production of surface enzyme systems and organic acid exudates.”
In other words, it is entirely possible, if not likely, that plants in a carbon dioxide enriched environment will develop the means to more effectively utilize available nutrient supplies.
Mycorrhiza are actually two different entities, a plant and a fungus, existing in a symbiotic or mutually beneficial relationship. Various kinds of fungus associate themselves with a particular plant through the root system. It has been found that the mycelium of the fungus can perform a number of functions beneficial to the plant, for example, accessing sources of phosphorous unavailable to the plant alone. It has been found that plants in association with mycorrhizal fungus are more resistant to diseases and the effects of drought. Mycorrhizal fungi are important in the colonization of barren or desolate landscapes that have been devastated by catastrophic floods, fires, or volcanic eruptions, and provide greater protection for plants growing in soils with high metal or acid concentrations.
Mahli and Grace call attention to one of the important variables in the response of plants to rising CO2: If plants become more efficient in the process of nutrient uptake, it mitigates one of the limiting factors of plant response to increased carbon dioxide concentrations. In many of the hundreds of studies conducted on plant response to increased carbon dioxide, nutrient availability, along with availability of light, was most frequently the limiting factor in the plants’ exploitation of carbon dioxide conferred advantages. If this turns out to be true, that plants gain improved means of accessing nutrients in the soil, thereby increasing their bulk mass available for carbon uptake, then, as Mahli and Grace point out: “A small steady increase in forest productivity can produce a large net C sink.” In other words, the increase in biomass increases the ability of the forest to consume more carbon dioxide from the atmosphere transforming it into greater plant mass. The increased growth and plant mass, the forest in turn consumes even more carbon dioxide in a positive feedback loop, removing it from the atmosphere in the process.
Mahli and Grace presented a table displaying the net biotic carbon sink in tropical regions based on the results of the Large Scale Biosphere-Atmosphere Experiment (LBA) that not only looked at Amazonia, but Costa Rica and Southeast Asia as well. However, the implications of the results of the LBA were considered problematic by the authors who state that: “The total predicted tropical C sink is 4.5 Gt C year—1 (4.5 billion tons per year) . . . This seems implausible unless there are ‘missing sources’ in the global C budget that are currently neglected.” Once again, we have the problem of the disappearing carbon. Let’s return to the question of carbon dioxide sources and sinks with which we began this essay.
Back to the Sink: Forests and Carbon Dioxide
4.5 Gt per year would amount to almost two-thirds of all the CO2 emitted annually through fossil fuel combustion. Is it possible that tropical forests are consuming this much carbon dioxide?
To understand this question better, the authors suggested that an alternative approach to detecting carbon uptake was to examine long-term forestry plots to see if there was evidence for increased biomass. To this end they turned to the work of O.L. Phillips et al., whose research report was published in the journal Science in 1998. Quoting from Phillips et al.:
“A recent study compiled data from forest inventories across 68 sites in apparently undisturbed tropical forests. It found large variability between plots, but reached a remarkable conclusion – most South American forests have increased in biomass in recent decades and have been accumulating C in biomass at a rate of 0.71 ± 0.39 t C ha-1 year-1.” [71 ± .39 tons of carbon per hectare per year]
Over the whole area of tropical forests, this translates into a total forest sink of some 2.0 gigatons of carbon per year of which at least half is in South America. So, according to these studies, tropical forests are taking up at about one-third of the amount of the carbon being released through fossil fuel consumption and they are responding with increased growth and biomass accumulation. This does not include the mid-latitude forests that are consuming a substantial amount of CO2 as well. In other words, Nature, with the help of Man, is initiating a rapid regeneration of tropical forests by exploiting the additional available carbon dioxide.
[pullquote]So, according to these studies, tropical forests are taking up at about one-third of the amount of the carbon being released through fossil fuel consumption and they are responding with increased growth and biomass accumulation. This does not include the mid-latitude forests that are consuming a substantial amount of CO2 as well. In other words, Nature, with the help of Man, is initiating a rapid regeneration of tropical forests by exploiting the additional available carbon dioxide.[/pullquote]
The Phillips et al. paper has some profound implications. They begin their paper by saying that: “Tropical forests contain as much as 40% of the C stored as terrestrial biomass and account for 30 to 50% of terrestrial productivity. Therefore, a small perturbation in this biome could result in a significant change in the global C cycle.” Their methodology involved compiling basal data on the cross-sectional area of trees per unit of ground area in mature tropical forest plots. The data was drawn from four tropical regions involving over 600,000 tree measurements. The results of Phillips et al. are consistent with the work of many other researchers and “are therefore indicative of a widespread increase in the biomass of surviving Neotropical forests over recent decades.”
They come to no firm conclusions as to what factors, natural or anthropogenic, might be driving this increase in biomass but consider increasing carbon dioxide as a possibility saying: “The biomass increase could also be a response to recent anthropogenic global change . . . Candidate factors for nutrient fertilization include increasing atmospheric CO2. . .” Finally, in addressing the problem of the missing sink, the authors put forward the idea that is laden with implications: “Our results suggest that mature Neotropical forest biomass may account for ~40% of the so-called ‘missing’ terrestrial C sink. Hence, intact forests may be helping to buffer the rate of increase in atmospheric CO2, thereby reducing the impacts of global climate change.” [see: Philllips, O. L. et al. (1998) Changes in the carbon balance of tropical forests: evidence from long term plots: Science, vol. 282 (Oct.18) pp. 439 – 442]
The same issue of Science contained a second article by a seven-member team describing a study of terrestrial carbon uptake in North America. The study utilized two atmospheric transport models incorporating data from 10 years’ worth of carbon dioxide samples collected from an array of atmospheric sampling stations. Using this data, spatial patterns indicative of the atmospheric distribution were developed and coupled with estimates of the ocean-atmosphere flux and the spatial distribution of fossil-fuel carbon dioxide emissions.
From this information it became possible to determine that spatial distribution of carbon uptake, and ascertain an estimate of net annual terrestrial sources and sinks. Looking at variances in the pattern of carbon uptake, the authors report that: “A large North American terrestrial uptake was estimated consistently for a range of spatiotemporal patterns assumed for the terrestrial uptake.” This large-scale intake of carbon dioxide by North American vegetation is attributed to a number of factors, including regrowth of abandoned farmland and previously logged forests, with this process being enhanced by nitrogen deposition, CO2 fertilization, and a mild increase in temperature. [see: Fan, S., M. Gloor, J. Mahlman, S. Pacala, J. Sarmiento, T Takahashi, P. Tans (1998) A Large Terrestrial Carbon Sink in North America Implied by Atmospheric and Oceanic Carbon Dioxide and Models: Science, vol. 282 (Oct. 16) pp. 442 – 446]
Both model simulations yielded more remarkable results. It was found that North America’s contribution to the annual uptake of carbon dioxide was about 1.7 billion tons. Given that the estimate of the annual North American emissions of CO2 by both the United States and Canada is about 1.6 billion tons, the implication is that North American vegetation is consuming each year more carbon dioxide than is being released through the burning of fossil fuel in North America!
[pullquote]Both model simulations yielded more remarkable results. It was found that North America’s contribution to the annual uptake of carbon dioxide was about 1.7 billion tons. Given that the estimate of the annual North American emissions of CO2 by both the United States and Canada is about 1.6 billion tons, the implication is that North American vegetation is consuming each year more carbon dioxide than is being released through the burning of fossil fuel in North America! [/pullquote]
A commentary on the findings of this team was included in the October 16 issue of Science to address this incredible and unexpected result:
“As greenhouse warming experts try to predict how much of the world’s climate may heat up in the next century, they keep bumping up against a mystery: Where does much of the carbon dioxide pumped into the air actually end up? . . . In what is shaping up as one of the most controversial findings yet to emerge in the greenhouse gas debate, a team of researchers . . . present evidence that North America sops up a whopping 1.7 petagrams (1.7 billion tons) of carbon a year – enough to suck up every ton of carbon discharged annually by fossil fuel burning in Canada and the United States.”
“The CMC team acknowledges that its results strain credibility. ‘I have trouble quite believing’ the size of the sink, says Tans, adding that ‘We’re pushing the data pretty far.’ But, says Sarmiento, ‘we’ve really carefully analyzed the data in a lot of different ways.’ U.S. Geological Survey geochemist Eric Sundquist agrees: ‘The paper is a credible and rigorous interpretation of the available data.’
[see: Kaiser, Jocelyn (1998) Possibly Vast Greenhouse Gas Sponge Ignites Controversy: Science, vol. 282 (Oct. 16) pp. 386 – 387]
Obviously, these results have enormous implications relative to the whole global warming debate. And, just as obviously, “greenhouse warming experts” are not as omniscient as the mainstream press and varied promoters of propaganda would have us believe. It is time to recognize that the IPCC is NOT infallible, that the so-called “consensus” is a complete fiction, and, that an effort to impose a global regulatory scheme based upon uncertain science would be a certain blunder.
[pullquote]Obviously, these results have enormous implications relative to the whole global warming debate. And, just as obviously, “greenhouse warming experts” are not as omniscient as the mainstream press and varied promoters of propaganda would have us believe. It is time to recognize that the IPCC is NOT infallible, that the so-called “consensus” is a complete fiction, and, that an effort to impose a global regulatory scheme based upon uncertain science would be a certain blunder. [/pullquote]
But let us proceed.
The Earth is Greening
In 2005, a study of the Sahel region of sub-Saharan Africa utilizing the NOAA AVHRR (Advanced Very High Resolution Radiometer) sensing system, employing the Normalized Difference Vegetation Index (NDVI), was published in the peer-reviewed Journal of Arid Environments. In their abstract the authors summarize the situation:
“For the last four decades there has been sustained scientific interest in contemporary environmental change in the Sahel (the southern fringe of the Sahara). It suffered several devastating droughts and famines between the late 1960s and early 1990s. Speculation about the climatology of these droughts is unresolved, as is speculation about the effects of land clearance on rainfall and about land degradation in this zone. However, recent findings suggest a consistent trend of increasing vegetation greenness in much of the region. Increasing rainfall over the last few years is certainly one reason, but does not fully explain the change.” [see: Olsson, L.; L. Eklundh & J. Ardo (2005) A recent greening of the Sahel—trends, patterns and potential causes: Journal of Arid Environments, vol. 63, pp. 556-566]
The figure below is reproduced from Olsson et al. It shows the results of trend analysis from 1982 to 1999 across the Sahel and southern Sahara region of North Africa. The data was derived from 40 climate observation stations and shows the percent change during that time frame. In regards to this figure the authors state: “The increase shown in Fig. 1 is remarkable. . .”
Reproduced below is Figure 1:
In the conclusion to their paper the authors state: “the strong secular trend of increasing vegetation greenness over the last two decades across the Sahel cannot be explained by a single factor such as climate. Increasing rainfall does explain some of the changes but not conclusively.”
So what other factors might remain to explain this greening of what has been desert through most of historical times?
As evidence continues to mount the answer to that question has become undeniable.
[pullquote]So what other factors might remain to explain this greening of what has been desert through most of historical times?
As evidence continues to mount the answer to that question has become undeniable.[/pullquote]
In 2005 the journal Global Change Biology carried a report on trends in the vegetation cover of Australia. The lead author Randall J. Donahue is a research scientist with CSIRO Land and Water, and the Research School of Biological Sciences at the Australian National University. The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is a 101 year old Australian scientific and research body, under whose auspices this work was conducted. The other two authors, Tim R. McVicar and Michael L. Roderick, are affiliated with the same institutions. The papers abstract describes their method:
“Using Advanced Very High Resolution Radiometer data spanning 1981-2006 . . . we examine whether vegetation cover has increased across Australia . . . Results from an Australia-wide analysis indicate that vegetation cover has increased, on average, by 0.0007 per year – an increase of ~8% over the 26 years . . . Over the same period, Australian average annual precipitation increased by 1.3 mm yr—2 (up 7%) . . . Interestingly, where vegetation cover increased at water-limited sites, precipitation trends were variable indicating that this is not the only factor driving vegetation response. As Australia is a generally highly water-limited environment, these findings indicate that the effective availability of water to plants has increased on average over the study period . . . Regardless of what has been driving these changes, the overall response of vegetation over the past 2 -3 decades has resulted in an observable greening of the driest inhabited continent on Earth.” [see: Donohue, Randall J.; Tim R. McVicar & Michael L. Roderick (2009) Climate-related trends in Australian vegetation cover as inferred from satellite observations, 1981-2006: Global Change Biology, vol. 15, pp. 1025-1039.]
By the year 2013, Randall Donahue and his colleagues had expanded the scope of their research from Australia to the globe. Their update was presented in Geophysical Research Letters. While they do not specifically name carbon dioxide as a culprit in their earlier work, by this time they had become convinced that it is playing a dominant role in the observed greening. They comment:
“Satellite observations reveal a greening of the globe over recent decades. The role in this greening of the ‘CO2 fertilization’ effect—the enhancement of photosynthesis due to rising CO2 levels—is yet to be established. The direct CO2 effect on vegetation should be most clearly expressed in warm, arid environments where water is the dominant limit to vegetation growth. Using gas exchange theory, we predict that the 14% increase in atmospheric CO2 (1982-2010) led to a 5 to 10% increase in green foliage cover in warm, arid environments . . . Our results confirm that the anticipated CO2 fertilization effect is occurring alongside ongoing anthropogenic perturbations to the carbon cycle…”
“The increase in water use efficiency of photosynthesis with rising Ca [carbon dioxide] has long been anticipated to lead to increased foliage cover in warm, arid environments, and both satellite and ground observations from the world’s rangelands reveal widespread changes toward more densely vegetated and woodier landscapes. Our results suggest that Ca has played an important role in this greening trend and that, where water is the dominant limit to growth, cover has increased in direct proportion to the CO2-driven rise in Wp [water use efficiency of photosynthesis] . . . The CO2 fertilization cover effect warrants consideration as an important land surface process.”
The CO2 fertilization effect certainly does warrant consideration as an important land surface process – one that is clearly a net positive within the global terrestrial ecology. However, the reality is that among global warming promoters the subject of positive consequences is taboo – to even bring it up invites derision and condescension and charges of being a fossil fuel industry lackey. But such an attitude is, in reality, symptomatic of a combination of ignorance and arrogance, and an unwillingness to think outside the confines of one’s ideology.
Science Daily reported on the work of Donohue and his colleagues referenced above, after interviewing them about their work on the carbon fertilization effect. Among his comments, Donahue said this:
“On the face of it, elevated CO2 boosting the foliage in dry country is good news and could assist forestry and agriculture in such areas; however there will be secondary effects that are likely to influence water availability, the carbon cycle, fire regimes and biodiversity, for example . . . Ongoing research is required if we are to fully comprehend the potential extent and severity of such secondary effects.”
Absolutely we need more research, but it is also the case, based upon what we now know, that negative consequences of some of those secondary effects will be mitigated under a carbon dioxide enhanced atmosphere. For example, greater root mass means that the plant can reach deeper for water and nutrients; that it can consolidate and retain the soil against erosion more effectively; that it can survive the effects of fires more effectively, and would be less likely to uproot during an intense storm.
Evidence confirming a global biospheric recovery continues to accumulate. Another study was published in Nature, Climate Change in 2015 by a seven-member team that employed satellite-based passive microwave observation to estimate above ground biomass (ABC) whereas previous studies had utilized radar or optical observations. The authors make the point:
“The intensity of natural microwave radiation from the Earth is a function of its temperature, soil moisture and the shielding effect of water in above ground vegetation biomass.” This new method supported earlier findings. From their investigations the team learned that:
“From 2003 onwards, forests in Russia and China expanded and tropical deforestation declined. Increased ABC associated with wetter conditions in the savannahs or northern Australia and southern Africa reversed global ABC loss, leading to an overall gain, consistent with trends in the global carbon sink reported in recent studies.” [see: Liu, Yi Y. et al. (2015) Recent reversal in loss of global terrestrial biomass: Nature Climate Change, vol. 5 (May) pp. 470 – 474]
A 2016 study on carbon exchange fluxes in the Sahel region concluded that: “A budget for the entire Sahel indicated a strong C sink mitigating the global anthropogenic C emissions.” [see: Tagesson, Torbern, et al. (2016) Spatiotemporal variability in carbon exchange fluxes across the Sahel: Agricultural and Forest Meteorology, vol. 226-227 (Oct.) pp. 108-118]
It should be noted that the idea that the biosphere is acting as an important carbon dioxide sink, thereby reducing the amount in the atmosphere substantially over the long term, has generally been excluded from IPCC computerized projections of the future. But, here again, the evidence is mounting that as the density of the Earth’s vegetation increases so will the ongoing need for greater amounts of CO2 to stimulate photosynthesis, resulting in a positive feedback cycle.
Reinforcing this probable outcome is the work of Joseph M. Craine and Peter B. Reich, with the Department of Integrative Biology at the University of California, Berkelely, and the Department of Forest Resources at the University of Minnesota, respectively. Their work, published in 2001 in New Phytologist, looked at the longevity of leaves for ten grassland species under varying carbon dioxide concentrations and was able to demonstrate yet another positive effect. They write:
“Although many plant traits affect C and N cycles in an ecosystem, leaf longevity has a central role in determining litterfall, standing biomass, and net primary productivity (NPP). For example, increases in leaf longevity could increase the carbon gain of individual leaves . . . and therefore increase stand NPP.” [see: Craine, Joseph M. & Peter B. Reich (2001) Elevated CO2 and nitrogen supply alter leaf longevity of grassland species: New Phytologist, vol. 150, pp. 397 – 403)
In other words, by living longer the leaves of these plants would consume even more carbon dioxide. As the authors say in their concluding discussion: “All other things equal, the increase in leaf longevity due to elevated CO2 would lead to greater ecosystem carbon gain, assuming the leaves maintained positive net photosynthesis over the additional period.”
A 2014 study looked at long-term experimental forestry plots that were established in 1872 in Central Europe, the same year as the founding of the International Union of Forest Research Organizations. From then until the present day, now over 140 years, these plots were surveyed between 10 and 20 times. The authors of this new study, Hans Pretzsch and four others, used the data collected from these surveys to analyze growth trends. What they found was astounding:
“Based on the oldest existing experimental forest plots in Central Europe, we show that, currently, the dominant tree species Norway spruce and European beech exhibit significantly faster tree growth (+ 32 to 77%), stand volume growth (+ 10 to 30%) and standing stock accumulation (+ 6 to 7%) than in 1960 . . . Standing wood volume, mean diameter, dominant height and mean tree volume currently grow significantly faster than in the past . . . coinciding with an increase in resource supply (CO2, N), together with an extended growing season accompanied by changes in other climatic variables … present forest stands grow more rapidly, and accumulate a given standing volume earlier than comparable stands did a century ago.” [see: Pretzsch, Hans, et al. (2014) Forest stand growth dynamics in Central Europe have accelerated since 1870: NatureCommunications 5 : 4967 | DOI: 10.1038 / ncomms 5967 | www.nature.com /naturecommunications]
This study of forest plots that have been carefully surveyed and monitored for a period in excess of 140 years, revealed that the rate of forest growth itself has accelerated strikingly since 1960. Could this result be extrapolated to the global scale? [pullquote]This study of forest plots that have been carefully surveyed and monitored for a period in excess of 140 years, revealed that the rate of forest growth itself has accelerated strikingly since 1960. Could this result be extrapolated to the global scale? [/pullquote]
Recovery of the Biosphere and Popular Misconceptions
The authors of another 2016 study employ meta-analytic techniques to compare soil water content under both ambient and elevated CO2 concentrations with varying conditions of climate, vegetation, soil and so on. The research was based upon 1705 field measurements sampled from 21 separate sites widely dispersed across 8 countries and published in 45 independent studies. In the abstract to this report the authors concede the now unavoidable conclusion:
“While recent findings based on satellite records indicate a positive trend in vegetation greenness over global drylands, the reasons remain elusive. We hypothesize that enhanced levels of atmospheric CO2 play an important role in the observed greening through the CO2 effect on plant water savings and consequent available soil water increases.”
The authors begin their paper by defining and describing the phenomenon of drylands:
“Defined broadly as zones where mean annual precipitation is less than two-thirds of potential evaporation, drylands are critically important systems and represent the largest terrestrial biome on the planet. Climate change, increasing populations and resulting anthropogenic effects are all expected to impact dryland regions over the coming decades. Considering that approximately 90% of the more than 2 billion people living in drylands are geographically located within developing countries, improved understanding of these systems is an international imperative.” [see: Lu, Xuefei; Lixin Wang & Matthew F. McCabe (2016) Elevated CO2 as a driver of global dryland greening: Nature.com/scientific reports (Feb. 12)]
Certainly the reoccurrences of drought and famine over the decades, especially in sub-Saharan Africa, have repeatedly underscored the importance of improved understanding as an international imperative.
But then the authors go on to describe the extraordinary developments beginning to manifest on planet Earth that could change the entire equation in profound ways:
“Recent regional scale analyses using satellite based vegetation indices such as the Normalized Difference Vegetation Index (NDVI), have found extensive areas of ‘greening’ in dryland areas of the Mediterranean, the Sahel, the Middle East and Northern China, as well as greening trends in Mongolia and South America. More recently, a global synthesis over the period 1982-2007 that used an integrated NDVI and annual rainfall, showed an overall ‘greening-up’ trend over the Sahel Belt, Mediterranean basin, China, Mongolia region and the drylands of South America.”
Pause for a minute and ponder what this research is saying. After years of a presumptive expansion of Earth’s deserts it is beginning to dawn upon researchers that something has changed – deserts are now contracting!
[pullquote]Pause for a minute and ponder what this research is saying. After years of a presumptive expansion of Earth’s deserts it is beginning to dawn upon researchers that something has changed – deserts are now contracting!
[/pullquote]
In various public forums and podcasts I have pointed out that the Earth’s deserts are actually contracting. In response to presenting this information various “critics” have typically said something to the effect that everybody “knows” that deserts are expanding around the world, and therefore I don’t know what I am talking about, and since I don’t know what I am talking about regarding that one thing, anything else I might have to say can be dismissed or ignored as well!
The idea of popular misconceptions regarding the status of Earth’s deserts was addressed recently in the Proceedings of the National Academy of Sciences in an article entitled “On regreening and degradation of Sahelian watersheds.” The study by Armel T. Kaptue and two colleagues at the Geospatial Sciences Center of Excellence, South Dakota State University, used satellite-derived vegetation indices in Senegal, Mali, and Niger from 1983 to 2012 to determine net primary production. As a preface to their work the authors explain that: “In the last 20 y, remote-sensing studies have documented an apparent increase in vegetation productivity in the Sahel using satellite measurements of vegetation greenness” (NDVI). But, while this has been going on, they further explain:
“Over many decades our understanding of the impacts of intermittent drought in water-limited environments like the West African Sahel has been influenced by a narrative of overgrazing and human-induced desertification. The desertification narrative has persisted in both scientific and popular conception, such that regional-recovery (“regreening”) . . . following the severe droughts of the 1970s—1980s, are sometimes ignored.”
And further
“in the popular press and often in the environmental and development literature, the reports are sometimes forgotten, to the extent that popular opinion . . . holds fast to pessimistic images of overgrazing, degradation, sand storms, and sand-dunes “marching” south from the Sahara towards the sea.” [see: Kaptue, Armel; Lara Prihodka, and Niall P. Hanan (2015) On regreening and degradation in Sahelian watersheds: Proceedings of the National Academy of Science, vol. 112, no. 39 (Sept. 29) pp. 12133-12138]
As I am criticized by various individuals who find the information I bring to the table unpalatable because it goes against their assumptions and unexamined beliefs, it is persistently apparent that most of them are simply regurgitating something they have heard, or read in popular accounts and assume, therefore, that they have enough knowledge to express an opinion on the matter. The degree of ignorance, the amount of misinformation and lack of critical thinking skills manifest in many of the remarks directed towards me in some of these public forums is symptomatic, I believe, of the sorry state of modern liberal education in America today. But that is a discussion for another place.
Another report by a 19 member international scientific team was published in 2016 that utilized two 30-year remote-sensing-based estimates of the northern hemisphere leaf area index (LAI) coupled with simulations from 19 Earth system models (ESMs). There is no ambiguity about the findings of this team:
“Significant land greening in the northern extratropical latitudes (NEL) has been documented through satellite observations during the past three decades. This enhanced vegetation growth has broad implications for surface energy, water and carbon budgets and ecosystem services across multiple scales. . . Our findings reveal that the observed greening record is consistent with an assumption of anthropogenic forcings, where greenhouse gases play a dominant role . . .”
“Where greenhouse gases play a dominant role.” In the conclusion to their report the authors state that:
“This study adds to an increasing body of evidence that the NEL has experienced an enhancement of vegetation activity, as reflected by increased trends in vegetation indices, aboveground vegetation biomass, and terrestrial carbon fluxes during the satellite era. Our analysis goes beyond previous studies . . . to establish that the trend of strengthened northern vegetation greening is clearly distinguishable from both the IV (internal variability) and the response to natural forcings alone. It can be rigorously attributed, with high statistical confidence, to anthropogenic forcings, particularly to rising concentrations of greenhouse gases.” [see: Mao, Jiafu; et al. (2016) Human-induced greening of the northern extratropical land surface: Nature Climate Change, Vol. 6 (Oct.) pp. 959 – 963]
The results of yet another study, conducted by a multidisciplinary, international team of scientists was published in 2016 in the journal Nature, Climate Change. This research confirms what is becoming apparent to a growing number of researchers around the world concerning the terrestrial effects of carbon dioxide enrichment. NASA’s website featured an account of the work of this team under the heading “Carbon Dioxide Fertilization Greening Earth, Study Finds.” The account proceeds to describe the work of the team:
“From a quarter to half of Earth’s vegetated lands has shown significant greening over the last 35 years largely due to rising levels of atmospheric carbon dioxide,” according to a new study published in the journal Nature, Climate Change on April 25. An international team of 32 authors from 24 institutions in eight countries led the effort, which involved using satellite data from NASA’s Moderate Resolution Imaging Spectrometer and the National Oceanic and Atmospheric Administration’s Advanced Very High Resolution Radiometer instruments to help determine the leaf area index, or amount of leaf cover, over the planet’s vegetated regions. See NASA’s website at https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fertilization-greening-earth
The study involved computer simulations of each variable in turn that could be stimulating the observed greening. The team looked at global temperature change, land cover change, precipitation, sunlight, nitrogen and carbon dioxide. The conclusion reached after extensive analysis was that nitrogen was responsible for 9% of the effect while carbon dioxide contributed a whopping 70%. One of the lead authors of this study was Ranga Myneni whose work was discussed above. Lead author Zaichun Zhu, from Peking University, China, is quoted as saying that the greening “has the ability to fundamentally change the cycling of water and carbon in the climate system.” Co-author Shilong Piao of the College of Urban and Environmental Sciences at Peking commented: “While our study did not address the connection between greening and carbon storage in plants, other studies have reported an increasing carbon sink on land since the 1980s, which is entirely consistent with the idea of a greening Earth.”
[pullquote]The study involved computer simulations of each variable in turn that could be stimulating the observed greening. The team looked at global temperature change, land cover change, precipitation, sunlight, nitrogen and carbon dioxide. The conclusion reached after extensive analysis was that nitrogen was responsible for 9% of the effect while carbon dioxide contributed a whopping 70%.[/pullquote]
In any case the article concludes with a little perspective on the matter:
“The greening represents an increase in leaves on plants and trees equivalent in area to two times the continental United States.”
This incredible phenomenon of planetary greening is of such considerable interest and importance that it is worth referring to the original Nature, Climate Change paper upon which NASA based their report for additional insight. In the abstract of that paper the authors describe their procedure and results:
“Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system . . . Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate 4 key drivers of LAI trends during 1982-2009. We show a persistent and widespread increase of the growing season integrated LAI (greening) over 25% to 50% of the global vegetated area . . . Factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (LCC) (4%). CO2 fertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau.” [See: Zhu, Zaichun, et al. (2016) Greening of the Earth and its drivers: Nature, Climate Change, Vol. 6, August, pp. 791 – 796]
[pullquote]“The greening represents an increase in leaves on plants and trees equivalent in area to two times the continental United States.” [/pullquote]
By using the phrase “climate change,” the authors are referring to the global increase in average temperature of about one degree in the past 150 years. The authors conclude their milestone paper with this statement: “Overall, the described LAI (leaf area index) trends represent a significant alteration of the productive capacity of terrestrial vegetation through anthropogenic influences.”
Let’s consider what this statement is saying.
The alteration of the productive capacity of terrestrial vegetation is a positive alteration, meaning that it is leading to MORE productive capacity for Earth’s vegetation, and this, as they readily admit, is happening as the result of anthropogenic influences. In other words, by consuming fossil fuel and releasing carbon dioxide into the atmosphere, we humans are increasing the productive capacity of Earth’s vegetation.
More soon,
Randall Carlson
If you would like to help us continue to produce independent media without commercial advertising please visit our store!
Your purchases, monthly subscriptions and donations help us to continue providing this paradigm shifting knowledge to the world.
Featured Products
Way cool! Some extremely valid points! I appreciate you writing this post cialis da Italia and the rest of the is extremely good. Another reason some people prefer Sildenafil, compared to Levitra or http://www.laneuvilleroy.fr/it.php
