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Picture Courtesy: https://www.downtoearth.org.in/news/climate-change/warming-planet-may-transform-tundra-ecosystems-from-carbon-sinks-to-sources-95717

Context: According to a recent study warming temperatures in arctic and alpine tundra ecosystems are increasing ecosystem respiration, which is releasing carbon into the atmosphere and potentially transforming these environments from carbon sinks to carbon sources.

Climate Change and its Impact on Tundra Ecosystems

• Tundra ecosystems are characterised by low temperatures, short growing seasons, and permafrost (frozen soil) that underlies much of the landscape.
• They are typically found in Arctic and alpine regions and are home to unique plant and microbial communities adapted to cold and harsh conditions.

Carbon Dynamics in Tundra Ecosystems

• Historically, tundra ecosystems have acted as carbon sinks, meaning they absorb more carbon from the atmosphere than they release. This is primarily due to the accumulation of organic carbon in frozen soils over time.

Factors Influencing Carbon Storage ●Permafrost: Permafrost stores vast amounts of organic matter (carbon) because decomposition rates are slow in frozen conditions. ●Vegetation: Tundra vegetation (e.g., mosses, lichens, shrubs) also sequesters carbon through photosynthesis and contributes to soil organic matter.

Impact of Warming on Tundra Ecosystems

Temperature Increase

• Warming temperatures associated with climate change are causing permafrost to thaw.
• Warmer temperatures extend the growing season and promote plant growth.

Biogeochemical Changes

• Rising temperatures alter soil conditions, affecting nutrient availability (e.g., nitrogen levels), soil moisture, and pH.
• These changes influence the activity of microbes responsible for decomposing organic matter.

Ecosystem Respiration and Carbon Release

Ecosystem Respiration

• Ecosystem respiration refers to the release of carbon dioxide (CO2) by all living organisms within an ecosystem, including plants, microbes, and soil organisms.
• As temperatures warm, metabolic rates of plants and microbes increase, leading to higher respiration rates.

Increased Metabolic Activity

• Warming temperatures stimulate plant growth and microbial activity.
• Plants and microbes respire more, breaking down organic matter and releasing CO2 into the atmosphere.

Experimental Insights ●Open-Top-Chamber Experiments: Researchers conducted long-term experiments using open-top chambers to simulate warming. Results showed that even modest temperature increases (1.4°C in air, 0.4°C in soil) led to a substantial increase (30%) in ecosystem respiration during the growing season. ●Sensitivity to Environmental Changes: Tundra regions with higher nitrogen limitations or increased turnover of plant and microbial communities are more sensitive to warming. These regions exhibit stronger respiration responses, indicating complex interactions between climate change and local environmental conditions.

Implications and Climate Modeling

• Shift to Carbon Source: The findings suggest that tundra ecosystems may transition from carbon sinks to carbon sources under continued warming. Increased respiration rates could lead to significant carbon release into the atmosphere, further exacerbating climate change.
• Need for Integrated Models: Understanding the linkages between soil nitrogen, carbon dynamics, and respiration responses is crucial for developing accurate climate models. Incorporating these findings into models will improve predictions of future carbon emissions and their impact on global climate.

Conclusion

• The study highlights the complex interactions between climate change, biogeochemical processes, and ecosystem dynamics in tundra environments. The transition of tundra ecosystems from carbon sinks to potential carbon sources highlights the urgent need for comprehensive research and modelling to inform climate mitigation strategies and policy decisions.

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Source:

Down to Earth

PRACTICE QUESTION Q. Geoengineering refers to technological interventions aimed at manipulating the climate.  While some geoengineering proposals might offer ways to mitigate warming, they also raise ethical concerns and potential risks of unintended consequences. Discuss the potential benefits and drawbacks of geoengineering as a response to climate change, considering the moral hazard of potentially relying on it as a crutch while delaying efforts to reduce emissions.