Nonlinear Earth System Dynamics Determine Biospheric Structure and Function: I—A Primer on How the Climate System Functions as a Heat Engine and Structures the Biosphere

The Earth’s climate system exhibits nonlinear behavior driven by interactions among the atmosphere, oceans, cryosphere, land, and biosphere. These dynamics have given rise to relatively stable environments that shape the structure and function of the modern biosphere. This review is a primer for conservation practitioners and natural resource managers to develop a deep understanding of how the Earth System works. The key is to recognize that shifts in Earth System dynamics due to global climate change can destabilize the biosphere in unforeseen ways. The potential emergence of novel ecoregions must be a critical factor in adaptation planning for conservation and resource management. We review how thermodynamic constraints and global circulation dynamics determine the distribution of terrestrial and marine biomes. These dynamics stem from the Earth System functioning as a heat engine, transporting excess heat from low to high latitudes. We illustrate how biome climates are organized into climate regimes, with spatial and temporal characteristics linked to complex features of atmospheric and oceanic circulation. At centennial to millennial scales, these dynamics have created a stable envelope of natural variability in climate that has established a long-standing operating space for biota. However, this stability is becoming increasingly uncertain due to the growing positive energy imbalance in the Earth System primarily driven by anthropogenic greenhouse gas emissions. This forcing is leading to disruptive climatic change, putting the biosphere on a trajectory toward new transient states. Such global to regional climatic instability and biospheric restructuring introduce a high level of uncertainty in ecological futures, with major implications for natural resource management, biodiversity conservation strategies, and societal adaptation. We conclude by discussing frameworks for impact assessments and decision making under climate uncertainty.