Scientists develop new methods to measure human impact on Earth’s critical zone

Protection of Earth's critical zone is key to ensuring future food security

With increasing impact of climate change across the world, food security has become a critical issue for the world and new research published by British and Chinese scientists says that future plans to tackle the climate change’s impacts on food security must integrate local knowledge to help preserve the Earth’s critical zone.

The critical zone is the thin layer of the planet’s surface that stretches from the roots of drinking water aquifers to the tops of plants and trees. It supports and sustains animal, and plant life by regulating the flow of water, greenhouse gases, nutrients and energy. Access to food, drinking water and clean air depend on a well-functioning critical zone, but decades of human activity have degraded the zone’s condition around the world.

In a paper published in the American Geophysical Union’s journal Earth’s Future, researchers from the UK and China outline how their experience of working with farmers on land heavily altered by human activity has shown how the critical zone can be better managed and protected.

According to a press statement, their insights are summarised in a new diagram, which seeks to visually convey human impact on the Earth’s critical zone more clearly than ever before. The researchers suggest that the new diagram should replace a widely used, more simplified graphic, introduced in 2007, which focused on the natural processes that shape the critical zone without addressing human impact on landscapes.

The statement adds that the new diagram is intended for use by academics across a range of fields for research and teaching purposes, by government agencies that fund science and landscape management, and in fundamental teaching resources such as textbooks. It more clearly shows how human activities like farming, mining, forestry and industry can contaminate water, cause soil erosion, and pollute the atmosphere.

The statement adds that Professor Larissa Naylor, of the University of Glasgow’s School of Geographical & Earth Sciences, led the design of the new diagram and is the paper’s corresponding author.

“Humans have been heavily modifying the Earth for nearly 12,000 years now through agriculture, mining, forestry, and urbanisation. We have changed our environment to such an extent that we have created a new geological epoch through the alterations we’ve made to the critical zone. In this new era, which many now call the Anthropocene, the impacts of our activities permeate down through the soil into the geology deep below and up into the local atmosphere above, forcing natural cycles to change,” says Naylor.

“We can see the effects of those changes in faster rates of erosion that drive soil degradation, for example, or through the greenhouse gas emissions that cause climate change. This directly impacts the ecosystems that sustain human life, including the livelihoods of farmers and local communities,” says Ganlin Zhang of the Institute of Soil Science at the Chinese Academy of Sciences in Nanjing, China, who is a co-author of the report.

The statement adds that the need to refine and redesign the existing approach to critical zone science became apparent to the research team during work at the four critical zone observatories in China. In recent decades, a series of critical zone observatories, or CZOs, have been established around the world to act as ‘living labs’ for critical zone science.

Earth’s critical zone plays an important role in meeting United Nations Sustainable Development Goals

The researchers set out to see how policy changes from the Chinese government, which aimed to restore degraded landscapes and reduce the use of synthetic fertilisers, had affected the functioning of the land across the CZOs. They also conducted research to find out how the farmers learned about the new policies, shared information with each other on best practice, and adapted their approach to land management.

“Farmers and local communities are at the front line of local land management, with a wealth of knowledge about how to farm productively and sustainably in their home environment. We showed that this knowledge is vital to improving our scientific understanding of critical zone systems,” says Professor Jennifer Dungait, of the University of Exeter and Scotland’s Rural College (SRUC), who is joint lead author of the paper.

“High-quality critical zone science is vital to helping governments, charities, funders and other organisations make important decisions about how we can slow the degradation of natural systems so that it can cope better with the challenges of climate change,” says Professor Paul Hallett, of the University of Aberdeen, also a co-author.

“In order to help them make the best decisions, we need to draw on this local knowledge, working with communities to design and share interdisciplinary science in a way that directly benefits local communities and is understandable to general audiences. That’s what this new diagram sets out to do by making human impacts on the critical zone more clearly visible. Previous diagrams had focused on a theoretical, pristine natural environment, which were less engaged with the physical reality of heavily human-modified environments that are lived in and shaped by local communities,” says Naylor.

“The insights gained from our work with Chinese farmers have been key to developing our new conceptual diagram, which represents the wide array of human impacts on rural to peri-urban terrestrial landscapes. It more clearly demonstrates the fundamental role the human technosphere plays in shaping the Earth, its landscapes and the ecosystems that sustain life for humans and wildlife that provide critical life-sustaining functions, such as pollination,” says Professor Timothy Quine, of the University of Exeter, another co-author of the paper.

Naylor says that a key lesson learned is that local people show resilience in sustaining their livelihoods in stressed, degraded ecosystems and that this knowledge is fundamental to interpreting scientific results in human-modified landscapes.

“We simply can’t use critical zone science to properly deliver the United Nations’ Sustainable Development Goals and planetary health without involving local people, and without acknowledging the impact that humans have already had on the critical zone. Local knowledge will help ensure that critical zone science can effectively support sustainable socio-economic development by improving the ecosystems of places where people live and work,” she says.