Soil microbial effects on plant community responses to fire in longleaf pine savannas

Anita Simha and Gaurav Kandlikar

Trajectories of the Earth System in the Anthropocene

Steffen et al., 2018

We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be. If the threshold is crossed, the resulting trajectory would likely cause serious disruptions to ecosystems, society, and economies. Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System—biosphere, climate, and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values.

Stability landscape showing the pathway of the Earth System out of the Holocene and thus, out of the glacial–interglacial limit cycle to its present position in the hotter Anthropocene. The fork in the road is shown here as the two divergent pathways of the Earth System in the future (broken arrows). Currently, the Earth System is on a Hothouse Earth pathway driven by human emissions of greenhouse gases and biosphere degradation toward a planetary threshold at ∼2 °C, beyond which the system follows an essentially irreversible pathway driven by intrinsic biogeophysical feedbacks. The other pathway leads to Stabilized Earth, a pathway of Earth System stewardship guided by human-created feedbacks to a quasistable, human-maintained basin of attraction. “Stability” (vertical axis) is defined here as the inverse of the potential energy of the system. Systems in a highly stable state (deep valley) have low potential energy, and considerable energy is required to move them out of this stable state. Systems in an unstable state (top of a hill) have high potential energy, and they require only a little additional energy to push them off the hill and down toward a valley of lower potential energy

https://www.pnas.org/doi/full/10.1073/pnas.1810141115

Global Food Quantity and Diversity to Drop by More than Half with Our Accelerated Climate Warming

Paul Beckwith

The formal demography of kinship: Demographic stochasticity in the kinship network

Hal Caswell

Le hasard pris sur l'aile, préservé, reproduit par la machinerie de l'invariance et ainsi converti en ordre, règle et nécessité. Un processus totalement aveugle peut par définition conduire à n'importe quoi ; il peut même conduire à la vision elle-même.

Jacques Monod. 1970. Le Hasard et la Nécessité : Essai sur la philosophie naturelle de la biologie moderne, Paris, Éditions du Seuil, coll.