Exploring the limits: Long-term observations on terrestrial carbon sink efficiency

In this talk, I will examine the long-term capabilities of plants to mitigate climate change, focusing on the weakening efficiency of terrestrial carbon sinks. I will address the slowdown in the increase of terrestrial carbon-sink activity. Anthropogenic activities, such as elevated atmospheric CO 2 and nitrogen inputs, have historically enhanced plant photosynthesis and the carbon sequestration capabilities of vegetation. However, the analysis of long-term observations and experiments provide evidence suggesting that the effectiveness of these carbon sinks is diminishing due to limitations in nutrients, water, and heat, as well as other factors like fires, pollution, and reduced vegetation carbon residence time. These findings are consistent with the five laws of life proposed by Peñuelas and Baldocchi (2019): the law of the conservation of mass, energy cannot be created or destroyed in an isolated system, the entropy of any isolated system always increases, the information content is a power of the material size of its store with an exponent larger than one, and basic mechanisms such as natural selection, self-organization, and random processes (not driven by selection) drive evolution, generating the huge complexity of organisms and ecosystems. the law of the conservation of mass, energy cannot be created or destroyed in an isolated system, the entropy of any isolated system always increases, the information content is a power of the material size of its store with an exponent larger than one, and basic mechanisms such as natural selection, self-organization, and random processes (not driven by selection) drive evolution, generating the huge complexity of organisms and ecosystems. Long-term data has underscored the critical role terrestrial plants have historically played in mitigating climate change by assimilating a significant portion of CO2 emissions, thus buffering against more severe warming. Yet, these data also raise pressing concerns about how long this mitigation effect can persist as the efficiency of carbon sinks seems to be declining. The potential deceleration in atmospheric carbon fixation and its long-term implications for climate change mitigation are not well studied, and current models may overestimate the capacity of carbon sinks and underestimate the severity of future climate warming if such factors are not thoroughly accounted for. Therefore, in this talk I will advocate for more comprehensive, long-term studies and updated models that consider the evolving structure and functioning of plants to better predict and manage the planet's carbon balance and climate change mitigation efforts over extended periods.