Sustaining Earth's Critical Zone: Basic science and interdisciplinary solutions for global challenges

Earth’s Critical Zone (CZ), the thin outer veneer of our planet from the top of the tree canopy to the bottom of our drinking water aquifers that supports almost all human activity, is experiencing ever-increasing pressure from growth in human population and wealth. Within the next 4 decades, demand for food and fuel is expected to double along with a more than 50% increase in demand for clean water. Understanding, predicting and managing intensification of land use and associated economic services, while mitigating and adapting to rapid climate change and biodiversity decline, is now one of the most pressing societal challenges of the 21st century.

The international CZ science community addressed these challenges at an international workshop, convened November 9th-11th, 2011 at the University of Delaware, USA. Their report outlines specific CZ science advances that will be necessary, and documents the links between basic science advances in Earth surface processes and the global sustainability agenda. The overarching hypothesis is that accelerating changes in land use, atmospheric composition and climate are forcing rapid and profound changes in the continental surface that require an unprecedented intensity and scale of scientific observation and new knowledge to guide intervention.

Six priority science questions are identified briefly as follows and detailed in full on page 20 of this volume.

Long-Term Processes and Impacts

1. How has geological evolution and paleobiology established CZ ecosystem functions?
2. How do molecular-scale interactions between CZ processes influence the development of watersheds and aquifers as integrated ecological-geophysical units?
3. How can theory and data be combined from molecular- to global- scales in order to interpret past transformations of Earth’s surface and forecast CZ evolution? Short-Term Processes and Impacts
4. What controls the resilience, response and recovery of the CZ and its integrated geophysicalgeochemical- ecological functions to perturbations such as climate and land use changes?
5. How can sensing technology, e-infrastructure and modelling be integrated for simulation and forecasting of essential terrestrial variables? 6. How can theory, data and mathematical models from the natural- and social- sciences, engineering, and technology, be integrated to simulate, value, and manage Critical Zone goods and services?

Critical Zone Observatories (CZOs) are research field sites that provide a major international capability to advance the new knowledge that is required for sustainable management of the CZ. Some common features of current CZOs are a wide range of multidisciplinary expertise that is concentrated in order to deliver transformative science advances; a focus on process studies that are hypothesis driven; and a combination of empirical observation at multiple scales with mathematical modelling and simulation. The USA CZOs are developing advances in sensor technology and real-time data acquisition, integrated with data management, across a range of temporal scales. European CZOs are driving forward integration of science advances with social sciences and policy, and development of decision support tools for policy and management intervention.