Rapid Degradation of Global Lake Submerged Vegetation: Satellite Observations Reveal a Critical Period of Ecosystem Shift

Tech 2025-01-22 11:29:03 Source: Network

Rapid Degradation of Global Lake Submerged Vegetation: Satellite Observations Reveal a Critical Period of Ecosystem ShiftA recent study published in The Innovation by Chinese scientists reveals the rapid degradation of submerged vegetation in global lakes over the past three decades. Using satellite remote sensing data, the research team, led by Professor Duan Hongtao's group at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, identified climate change and human activities as key drivers of this phenomenon

A recent study published in The Innovation by Chinese scientists reveals the rapid degradation of submerged vegetation in global lakes over the past three decades. Using satellite remote sensing data, the research team, led by Professor Duan Hongtao's group at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, identified climate change and human activities as key drivers of this phenomenon.

The study utilized 1.4 million Landsat satellite images from 1989 to 2021 to develop a global monitoring method for aquatic vegetation in lakes. This enabled the reconstruction of a spatiotemporal dataset on the distribution of both emergent/floating-leaved vegetation (FEAV) and submerged vegetation (SAV) in 5,587 shallow lakes worldwide since 1990. This dataset provides valuable support for understanding global lake ecosystem changes.

Rapid Degradation of Global Lake Submerged Vegetation: Satellite Observations Reveal a Critical Period of Ecosystem Shift

The study found that between 1989 and 2021, the average global coverage of aquatic vegetation was 108,186 square kilometers, approximately 28.9% of the total global lake area. Ninety-five percent of this vegetation was located in the Northern Hemisphere, with the highest proportion in North America, followed by Asia and Europe. This detailed description of the geographical distribution of global lake aquatic vegetation laid the foundation for further analysis of its spatiotemporal changes.

However, the study's most striking finding is the contrasting trends in SAV and FEAV over the past few decades. Since 1990, global lake SAV showed an initial increase followed by a significant decline, while FEAV demonstrated an initial decrease followed by an increase, with a turning point around the year 2000.

More alarmingly, since 2000, global lake SAV has undergone rapid degradation, with a 30.4% reduction in coverage. In stark contrast, FEAV increased slowly, expanding by 15.6%. This trend became even more pronounced after 2010.

To better quantify and understand this ecosystem shift, the research team proposed a lake steady-state transition index, In(FEAV/SAV). This index indicates that around 2000 marked a critical period of global lake steady-state transition. Since then, the dominance of SAV has declined, while that of FEAV has increased, suggesting a shift towards a shadow state dominated by floating-leaved vegetation and a turbid state dominated by algae.

The driving factors behind this ecosystem shift differed across periods. Before 2010, human-induced eutrophication was the primary driver. Eutrophication, caused by excessive nutrients in the water, promotes algal blooms that inhibit SAV growth. However, since 2010, global warming has become the dominant factor. Increased temperatures, altered precipitation patterns, and more frequent extreme climate events associated with climate change have significantly impacted lake ecosystems, further accelerating SAV degradation.

Submerged vegetation, often referred to as "underwater forests," plays a crucial role in lake ecosystems. It enhances water clarity, provides habitat and food sources for fish and other aquatic organisms, and helps maintain biodiversity. The degradation of SAV not only directly impacts lake ecological functions but also negatively affects human societies reliant on these ecosystems, such as reduced fisheries yields and decreased water quality.

Compared to SAV, FEAV has different ecological effects. Its dense foliage can shade underwater vegetation, leading to simplified underwater communities. Therefore, the decrease in SAV and increase in FEAV often signify lake ecosystem degradation.

This research serves as a wake-up call regarding the health of global lake ecosystems. The research team emphasizes the need for effective strategies to protect the sustainable development of lake ecosystems. These strategies could include reducing nutrient pollution, controlling greenhouse gas emissions to mitigate climate change, and strengthening lake ecosystem protection and restoration efforts.

This study provides comprehensive data on the spatiotemporal distribution and changes of global lake aquatic vegetation, revealing the mechanisms of climate change and human activities on lake ecosystems and providing a scientific basis for developing effective lake protection and management strategies. Further research is needed to explore the specific mechanisms of change in different regions and lake types to develop more effective protection strategies. This is not only crucial for the health of lake ecosystems but also for the sustainable development of human society. In-depth research on the degradation of global lake submerged vegetation will contribute to a better understanding of global ecosystem changes and provide important scientific basis for formulating effective environmental protection policies. Continued monitoring and research are essential to maintaining global ecological balance and ensuring human well-being.

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