The study published in Nature Geoscience, titled “Sustained Greening of the Antarctic Peninsula Observed from Satellites,” focuses on the observed increase in vegetation, particularly moss-dominated ecosystems, on the Antarctic Peninsula (AP). While it attributes this “greening” to recent regional warming trends, the paper conspicuously neglects the broader global phenomenon known as carbon dioxide (CO2) fertilization or global greening, which has been documented worldwide. Instead, it takes a rather narrow and selective approach, focusing on the correlation between temperature rise and greening in this specific cold-climate ecosystem, largely ignoring the established role of CO2 in enhancing plant growth globally.

Abstract

The Antarctic Peninsula has experienced considerable anthropogenic warming in recent decades. While cryospheric responses are well defined, the responses of moss-dominated terrestrial ecosystems have not been quantified. Analysis of Landsat archives (1986–2021) using a Google Earth Engine cloud-processing workflow suggest widespread greening across the Antarctic Peninsula. The area of likely vegetation cover increased from 0.863 km² in 1986 to 11.947 km² in 2021, with an accelerated rate of change in recent years (2016–2021: 0.424 km² yr⁻¹) relative to the study period (1986–2021: 0.317 km² yr⁻¹). This trend echoes a wider pattern of greening in cold-climate ecosystems in response to recent warming, suggesting future widespread 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 cold regions like the Antarctic Peninsula could easily be explained as part of the broader CO2-driven global greening trend, which has been observed across a variety of ecosystems, from tropical forests to temperate and boreal regions. Global greening is not just limited to cold-climate ecosystems; rather, it’s a pervasive effect driven by increased atmospheric CO2, which enhances plant growth efficiency through a process known as carbon fertilization. Yet, the authors of this study appear to cherry-pick data and studies focusing almost exclusively on temperature as the driver of this greening, while downplaying or ignoring the impact of CO2 enrichment, a factor that has been widely accepted in the scientific community.

The Premise of the Study and Its Narrow Focus on Temperature

The core premise of the study is that the observed greening of the Antarctic Peninsula over recent decades is primarily the result of warming driven by anthropogenic climate change. The authors reference warming trends over the past 60 years, particularly on the West Antarctic and Antarctic Peninsula, regions that have experienced some of the fastest temperature increases globally. They highlight that despite a pause in warming between 1999 and 2014 due to natural variability, the long-term warming trend is projected to continue at 0.34°C per decade until 2100​.

The study uses satellite data from 1986 to 2021, applying normalized difference vegetation index (NDVI) and Tasseled Cap Greenness (TCG) as proxies for vegetation cover. Their analysis suggests a significant increase in moss-dominated ecosystems, with vegetation cover expanding from 0.863 km² in 1986 to 11.947 km² in 2021, and an accelerated rate of change in recent years (2016–2021) compared to the overall study period​.

The authors link this greening primarily to temperature increases, citing the lengthening of growing seasons, warmer conditions, and increased moisture availability due to reductions in sea ice extent. However, they make only cursory mention of the larger, well-established phenomenon of CO2 fertilization and its role in global plant productivity increases.

Ignoring the Evidence for Global CO2 Fertilization

One of the major shortcomings of this study is its failure to consider or adequately address the global impact of increased atmospheric CO2 concentrations, which are well known to enhance plant growth across a wide range of ecosystems. The phenomenon of CO2 fertilization has been extensively documented in studies like the one by Zhu et al. (2016), which found that global leaf area increased by over 10% in the past two decades, largely driven by CO2 enrichment​.

The Antarctic Peninsula, though a unique and cold ecosystem, is not immune to the effects of global processes. The rise in atmospheric CO2 concentrations has been shown to enhance photosynthesis and water-use efficiency in plants, enabling them to thrive even in areas where water or temperature might otherwise be limiting factors. This is particularly relevant in cold, high-latitude ecosystems where the growing season is short, and any enhancement in plant productivity due to higher CO2 levels could have an outsized impact on vegetation cover.

The fact that the authors of this study chose to ignore this well-documented global trend raises questions about the selectivity of their analysis. While they acknowledge that warming temperatures may play a role in greening, they fail to adequately explore how increased CO2 levels could be contributing to the observed changes in vegetation cover on the Antarctic Peninsula. By focusing almost exclusively on temperature as the driver of greening, they present an incomplete picture of the underlying processes.

Cherry-Picking Temperature Data

Another issue with the study is the apparent cherry-picking of temperature data to support the claim that warming is the primary driver of greening. The authors note a “recent pause in warming” between 1999 and 2014 but argue that the overall trend is one of continued warming. However, this “pause” is more than a minor footnote—it suggests that temperature is not the only or even the primary factor driving changes in vegetation cover.

In fact, the recent slowdown in warming across the Antarctic Peninsula, linked to natural variability, challenges the notion that temperature alone is responsible for the observed greening. If warming had paused or even reversed during this period, one would expect a corresponding slowdown in greening. Yet, the study finds that the rate of greening has accelerated in recent years, suggesting that factors other than temperature are at play.

This brings us back to CO2 fertilization. Even during periods of stable or declining temperatures, plants can continue to thrive and expand their ranges due to increased atmospheric CO2, which enhances their photosynthetic capacity and water-use efficiency. The failure to consider this factor in the analysis is a glaring omission, especially when the authors attempt to attribute all observed greening to temperature increases.

The Global Context of Greening

To better understand the limitations of this study, it’s useful to place the findings in the context of global greening trends. The Earth’s land surface has been “greening” for several decades, with large increases in leaf area across tropical forests, savannas, and boreal regions​. This greening has been driven by a combination of factors, including CO2 fertilization, nitrogen deposition, and land-use changes, with CO2 enrichment being the dominant factor.

Even in high-latitude regions, such as the Arctic and Antarctic, where temperatures have risen faster than the global average, CO2 fertilization plays a critical role. In these cold environments, the growing season is short, and any increase in photosynthetic efficiency can have a significant impact on vegetation cover. For example, in the Arctic, researchers have documented a similar greening trend, which has been attributed to both warming temperatures and increased CO2 availability​.

The failure of the authors to engage with this broader body of literature on global greening and CO2 fertilization creates a skewed narrative. By attributing the greening of the Antarctic Peninsula almost exclusively to temperature increases, they overlook the more comprehensive explanation provided by global trends in plant productivity and atmospheric CO2 concentrations.

Conclusions: A Narrow View of a Global Phenomenon

The study of the Antarctic Peninsula’s greening presents an interesting case of vegetation expansion in one of the planet’s coldest regions, but it suffers from a narrow and selective approach to explaining the phenomenon. By focusing almost exclusively on temperature as the driver of greening, the authors ignore the well-established global impact of CO2 fertilization, which has been shown to enhance plant growth across a wide range of ecosystems.

This selective focus on temperature is problematic for several reasons. First, it overlooks the fact that CO2 fertilization can drive plant productivity even in the absence of significant temperature increases. Second, it downplays the global context of greening, which has been observed in ecosystems ranging from tropical forests to Arctic tundra. Finally, by cherry-picking temperature data and ignoring periods of warming “pauses,” the authors present an incomplete picture of the factors driving vegetation change in the Antarctic Peninsula.

Ultimately, this study reflects a broader trend in climate science, where researchers often focus on temperature as the primary driver of environmental change while neglecting the significant role of CO2. While temperature undoubtedly plays a role in shaping ecosystems, it is only part of the story. The global greening phenomenon, driven by increased atmospheric CO2, is a critical factor that must be considered in any comprehensive analysis of vegetation change, whether in the Antarctic or elsewhere. It’s difficult to believe the level of myopia demonstrated by these experienced researchers was not intentional.