Emerging from the warehouse of knowledge about terrestrial ecosystem functioning and the application of the systems ecology paradigm, exemplified by the power of simulation modeling, tremendous strides have been made linking the interactions of the land, atmosphere, and water locally to globally. Through integration of ecosystem, atmospheric, soil, and more recently social science interactions, plausible scenarios and even reasonable predictions are now possible about the outcomes of human activities. The applications of that knowledge to the effects of changing climates, human-caused nitrogen enrichment of ecosystems, and altered UV-B radiation represent challenges addressed in this chapter. The primary linkages addressed are through the C, N, S, and H2O cycles, and UV-B radiation. Carbon dioxide exchanges between land and the atmosphere, N additions and losses to and from lands and waters, early studies of SO2 in grassland ecosystem, and the effects of UV-B radiation on ecosystems have been mainstays of research described in this chapter. This research knowledge has been used in international and national climate assessments, for example the IPCC, US National Climate Assessment, and Paris Climate Accord. Likewise, the knowledge has been used to develop concepts and technologies related to sustainable agriculture, C sequestration, and food security.

Introduction

Terrestrial ecosystems provide a number of key services to society that are linked to carbon (C) cycle processes, a few of which include controlling food and fiber production, basic building materials, energy sources, and soil water holding capacity. Human societies have developed a number of land-use practices to enhance biological C processes and increase the delivery of many ecosystem services. However, some of the modifications have led to unintended degradation of land systems in ways that have reduced the natural capacity of ecosystems to maintain a range of supporting, provisioning, and regulating services.

As society strives to sustain key ecosystem services while attempting to meet the challenge of a growing human population and manage for climate change, new and sustainable land-use strategies must play a role. Sustainable management practices – those that maintain the provision of ecosystem services at or from a location – should be a main component of any land-use strategy if we are to successfully deal with global environmental challenges. Society is now demanding much more from land-use systems to achieve multiple goals. Multiple ecosystems services are being required from these systems – to provide food, environments for maintaining biodiversity, and production of energy products, and for preventing pollutants from entering the air and waterways. Developing land-system practices and policies that consider the long-term dynamics of C cycling among competing ecosystem services will provide a framework to develop more sustainable land management.