The study was published in natural geosciencesEntitled “Continued greening of the Antarctic Peninsula as observed from satellites,” it focuses on the observed increase in vegetation on the Antarctic Peninsula (AP), specifically moss-dominated ecosystems. While the paper attributes this “greening” to recent regional warming trends, it notably ignores the broader global phenomenon known as carbon dioxide (CO2) fertilization, or global greening, which has been documented around the world . Instead, it takes a rather narrow and selective approach, focusing on the correlation between rising temperatures and greening in this particular cold-climate ecosystem, largely ignoring the established role of carbon dioxide in promoting plant growth globally .
abstract
The Antarctic Peninsula has experienced severe anthropogenic warming in recent decades. While the cryosphere response is well defined, the response of moss-dominated terrestrial ecosystems has not yet been quantified. Analysis of the Landsat archive (1986-2021) using the Google Earth Engine cloud processing workflow shows widespread greening across the Antarctic Peninsula. Possible vegetation cover increased from 0.863 km²2 11.947 kilometers in 19862 2021. The pace of change has accelerated in recent years (2016-2021: 0.424 km)2Year−1) relative to the study period (1986–2021: 0.317 km2Year−1). This trend echoes broader greening patterns in cold climate ecosystems in response to recent warming, suggesting widespread future changes in the Antarctic Peninsula's terrestrial ecosystems and their long-term functioning.
https://www.nature.com/articles/s41561-024-01564-5
This omission is significant because the greening of colder regions like the Antarctic Peninsula could easily be explained as part of a broader CO2-driven global greening trend that occurs in a variety of ecosystems from tropical forests to temperate and boreal regions. were observed. Global greening is not limited to cold-climate ecosystems; rather, it is a widespread effect driven by increased levels of carbon dioxide in the atmosphere, which increases plant growth efficiency through a process called carbon fertilization. However, the study's authors appear to have cherry-picked data and studies that almost exclusively focus on temperature as the driver of this greening, while downplaying or ignoring the impact of carbon dioxide concentration, a factor widely accepted by the scientific community.
The premise of the study and its narrow focus on temperature
The core premise of the study is that the greening of the Antarctic Peninsula observed in recent decades is largely the result of warming driven by anthropogenic climate change. The authors refer to warming trends over the past 60 years, particularly in West Antarctica and the Antarctic Peninsula, which have experienced some of the fastest temperature rises in the world. They highlight that despite a pause in warming between 1999 and 2014 due to natural variability, the long-term warming trend is expected to continue at 0.34°C per decade until 2100.
The study used satellite data from 1986 to 2021 and applied the normalized difference vegetation index (NDVI) and tasseled cap greenness (TCG) as proxy indicators of vegetation cover. Their analysis showed a significant increase in moss-dominated ecosystems, with vegetation coverage expanding from 0.863 square kilometers in 1986 to 11.947 square kilometers in 2021, and in recent years (2016-2021) compared with the entire study period The rate of change is accelerating.
The authors link this greening primarily to rising temperatures, citing lengthening growing seasons, a warmer climate, and increased moisture availability due to reduced sea ice extent. However, they only briefly mention the broader, established phenomenon of carbon dioxide fertilization and its role in increasing plant productivity worldwide.
Ignoring the evidence of global carbon dioxide fertilization
One of the study's major shortcomings is that it fails to consider or overaddresses the global impacts of increasing atmospheric carbon dioxide concentrations, which are known to promote plant growth in a wide range of ecosystems. The phenomenon of carbon dioxide fertilization has been extensively documented in studies by Zhu et al. (2016), which found that global leaf area has increased by more than 10% over the past two decades, primarily due to carbon dioxide concentration.
Although the Antarctic Peninsula is a unique and cold ecosystem, it is not immune to global processes. Rising concentrations of carbon dioxide in the atmosphere have been shown to enhance photosynthesis and water use efficiency in plants, allowing them to thrive even in areas where water or temperature may be limiting factors. This is particularly important in cold high-latitude ecosystems, where the growing season is short and any increase in plant productivity due to elevated carbon dioxide levels could have a dramatic impact on vegetation cover.
The fact that the study's authors chose to ignore this well-documented global trend raises questions about the selectivity of their analysis. While they acknowledged that rising temperatures may play a role in greening, they failed to fully explore how rising carbon dioxide levels contributed to the observed changes in vegetation cover on the Antarctic Peninsula. By focusing almost exclusively on temperature as a driver of greening, their description of the underlying processes is incomplete.
Select temperature data
Another problem with this study is the apparent cherry-picking of the temperature data to support the claim that warming is the main driver of greening. The authors note a “recent pause in warming” between 1999 and 2014, but argue that the overall trend is continued warming. However, this “pause” is more than a minor footnote – it shows that temperature is not the only or even the main factor driving changes in vegetation cover.
Indeed, the recent slowdown in warming on the Antarctic Peninsula has been linked to natural variability, challenging the idea that temperature alone is responsible for the observed greening. If warming stops or even reverses during this period, one would expect greening to slow accordingly. However, research has found that greening has accelerated in recent years, suggesting factors other than temperature are also at play.
Which brings us back to CO2 fertilization. Even during periods of stable or declining temperatures, plants continue to grow and expand their range due to increased levels of carbon dioxide in the atmosphere, thereby enhancing their photosynthetic capabilities and water use efficiency. The failure to account for this factor in the analysis is a glaring omission, especially when the authors attempted to attribute all observed greening to rising temperatures.
global greening background
To better understand the limitations of this study, it is useful to place the findings within the context of global greening trends. The Earth's land surface has been “greening” for decades, with dramatic increases in foliage in tropical forests, savannahs and boreal regions. This greening is driven by a combination of factors, including carbon dioxide fertilization, nitrogen deposition and land use change, with carbon dioxide enrichment being the dominant factor.
Even in high latitudes, such as the Arctic and Antarctic, where temperatures are rising faster than the global average, carbon dioxide fertilization plays a crucial role. In these cold environments, where the growing season is short, any increase in photosynthetic efficiency will have a significant impact on vegetation cover. In the Arctic, for example, researchers have documented similar greening trends, which have been attributed to warming temperatures and increased carbon dioxide availability.
The authors' failure to delve into the broader literature on global greening and CO2 fertilization creates a distorted narrative. They attribute the greening of the Antarctic Peninsula almost entirely to rising temperatures, ignoring the fuller explanation provided by global trends in plant productivity and atmospheric carbon dioxide concentrations.
Conclusion: A narrow view of a global phenomenon
Research on the greening of the Antarctic Peninsula presents an interesting case of vegetation expansion in one of the coldest regions on Earth, but it takes a narrow and selective approach to explaining the phenomenon. The authors focus almost exclusively on temperature as a driver of greening, ignoring the established global impact of CO2 fertilization, which has been shown to promote plant growth in a wide range of ecosystems.
This selective focus on temperature is problematic for several reasons. First, it ignores the fact that CO2 fertilization can increase plant productivity even in the absence of significant temperature increases. Second, it downplays the global context of greening, which is observed in ecosystems from tropical forests to arctic tundra. Finally, by cherry-picking temperature data and ignoring periods of “pauses” in warming, the authors provide an incomplete picture of the factors driving vegetation change on the Antarctic Peninsula.
Ultimately, the study reflects a broader trend in climate science, in which researchers often focus on temperature as the main driver of environmental change while ignoring the important role of carbon dioxide. While temperature undoubtedly plays a role in shaping ecosystems, it's only part of the story. Global greening caused by increased levels of carbon dioxide in the atmosphere is a key factor that must be considered in any comprehensive analysis of vegetation change, whether in Antarctica or elsewhere. It is hard to believe that the degree of myopia displayed by these experienced researchers was not intentional.
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