Humans as geomorphic agents: including humans in critical zone science to enhance Anthropocene landscape sustainability

Critical Zone Observatories (CZOs) explore the deep evolution of landscapes from the bottom of groundwater to the top of vegetation, representing a bridge between geology, geomorphology and ecology. Human impacts on the landscape, notably agriculture and urbanisation, are key drivers of terrestrial landscape change, with these challenges providing a focus of a new class of 3^rd generation Critical Zone Observatories (CZOs).  Four of these CZOs were established in China to understand how environmental processes, from the top of vegetation through 10’s to 100’s of metres of soil to bedrock, interact and are affected by land management.  The China CZOs cover vastly different geomorphological settings in karst, loess, and red soil environments that encompass over 1/3 of China’s land area and support 25% of the population. The 4^thCZO lies in the peri-urban coastal zone, reflecting urban migration that is growing in China, with over 1/6 of China’s population already migrated from rural areas and 52% of the population in cities.

This talk provides an overview of key geomorphologically relevant findings from these CZOs, obtained by a team of over 50 principal-/co-investigators and many other postdoctoral scientists and students. An over-arching theme is integrating humans into critical zone science to tackle threats to landscape tipping points being crossed, impacting on food and environmental security.  While 2^nd generation CZOs capture human impact, the role of human decision-making has been largely overlooked. A 3^rd generation approach to CZ science emerged from the China-UK CZO programme (2016-2020). Here, human geography informed knowledge exchange research complemented traditional multidisciplinary CZ science. This provided novel insights into human-environment interactions (and humans as geomorphic agents) that aided the interpretation of empirical data and helped identify the greatest financial pressures on farmers that also adversely impact their local landscape. It also illustrates how scientific sampling in heavily human-modified landscapes can be adjusted to better incorporate the impacts of humans as geomorphic agents. The approach also identified how local people chose to learn more environmentally and economically sustainable farming methods, thereby guiding fit-for-purpose knowledge exchange activities between CZ scientists and key stakeholders. We thus outline the benefits of incorporating learnings about human behaviours and their beneficial impacts into CZO projects. We demonstrate that human geography needs to form a key dimension of multi-disciplinary CZ science approaches to enable identification of the mechanisms underlying human contributions and pressures on CZ functions. Crucially, deep understanding of impacts of environmental and economic stressors on human livelihoods can provide the rationale for policy and local action to achieve resilient social-ecological systems. We thus show how 3^rd generation CZOs that combine physical and human geography, underpinned by local knowledge, can provide practical feedback to communities in stressed environments, enabling better achievement of sustainable development goals and planetary health.