Ecosystems and the Biosphere as Complex Adaptive Systems

Simon Levin  

Plant domestication and agricultural ecologies  

Fuller et al., 2023.

Plant life defines the environments to which animals adapt and provides the basis of food webs. This was equally true for hunter-gatherer economies of ancestral humans, yet through the domestication of plants and the creation of agricultural ecologies based around them, human societies transformed vegetation and transported plant taxa into new geographical regions. These human–plant interactions ultimately co-evolved, increasing human population densities, technologies of farming, and the diversification of landraces and crop complexes. Research in archaeology on preserved plant remains (archaeobotany) and on the genomes of crops, including ancient genomes, has transformed our scientific understanding of the complex relationships between humans and plants that are entailed by domestication. Key realizations of recent research include the recognition that: the co-evolution of domesticates and cultures was protracted, the adaptations of plant populations were unintended results of human economies rather than intentional breeding, domestication took place in dozens of world regions involving different crops and cultures, and convergent evolution can be recognized among cropping types — such as among seed crops, tuber crops, and fruit trees. Seven general domestication pathways can be defined for plants. Lessons for the present-day include: the importance of diversity in the past; genetic diversity within species has the potential to erode over time, but also to be rescued through processes of integration; similarly, diversification within agricultural ecosystems has undergone processes of decline, including marginalised, lost and ‘forgotten’ crops, as well as processes of renewal resulting from trade and human mobility that brought varied crops and varieties together.

https://n9.cl/a0q172

Mycorrhizal mycelium as a global carbon pool 

Hawkins et al., 2023.

For more than 400 million years, mycorrhizal fungi and plants have formed partnerships that are crucial to the emergence and functioning of global ecosystems. The importance of these symbiotic fungi for plant nutrition is well established. However, the role of mycorrhizal fungi in transporting carbon into soil systems on a global scale remains under-explored. This is surprising given that ∼75% of terrestrial carbon is stored belowground and mycorrhizal fungi are stationed at a key entry point of carbon into soil food webs. Here, we analyze nearly 200 datasets to provide the first global quantitative estimates of carbon allocation from plants to the mycelium of mycorrhizal fungi. We estimate that global plant communities allocate 3.93 Gt CO2e per year to arbuscular mycorrhizal fungi, 9.07 Gt CO2e per year to ectomycorrhizal fungi, and 0.12 Gt CO2e per year to ericoid mycorrhizal fungi. Based on this estimate, 13.12 Gt of CO2e fixed by terrestrial plants is, at least temporarily, allocated to the underground mycelium of mycorrhizal fungi per year, equating to ∼36% of current annual CO2 emissions from fossil fuels. We explore the mechanisms by which mycorrhizal fungi affect soil carbon pools and identify approaches to increase our understanding of global carbon fluxes via plant–fungal pathways. Our estimates, although based on the best available evidence, are imperfect and should be interpreted with caution. Nonetheless, our estimations are conservative, and we argue that this work confirms the significant contribution made by mycorrhizal associations to global carbon dynamics. Our findings should motivate their inclusion both within global climate and carbon cycling models, and within conservation policy and practice.

https://n9.cl/x0ofm