Soil is one of the most species-dense habitats in existence. You can expect to find up to 1.5 kilograms of organisms, including roundworms, earthworms, springtails, mites, and insect larvae living under one square meter of healthy soil. These are joined by a wide variety of microorganisms such as bacteria, protists, and fungi. All of these creatures eat and transform living and dead animal and plant material into nutrients that become the basis for growth and new life. Without soil organisms, no plants would be able to grow and thus humans would not be able to survive. Soil biota quietly perform a range of services for humans behind the scenes –or in this case, below the ground.

Knowing this information makes it all the more astonishing that soils have hardly featured in international strategies for protecting biodiversity up to now. The authors of the new article in Science see this as a significant problem: “If we do not protect soils for the next generations, aboveground biodiversity and food production cannot be guaranteed either.” Their appeal goes out to the 196 nations who are currently negotiating a new strategy to protect biodiversity within the framework of the UN Convention on Biological Diversity (CBD).

Healthy soils are becoming increasingly rare. Many of the reasons for this are related to industrial agricultural practices, where soils are subjected to intensive cultivation with heavy machinery, fertilizers, and pesticides. Not only that, but they are also frequently compacted, built over, or lost due to wind and water erosion, while global warming is putting them under additional pressure. According to the Heinrich Böll Foundation in Germany, around 24 billion tons of fertile soil are lost worldwide every year. As a result, the many important environmental contributions of soil – including water purification and protection against plant diseases – are gradually deteriorating. Soils are also the most important carbon reservoir on earth and therefore help to slow global warming.

According to the researchers, these contributions are given far too little attention in the political debate surrounding conservation. “Up to now, soil conservation has been mostly reduced to the impacts related to soil erosion and its importance for agriculture,” says first author Dr. Carlos Guerra (iDiv, Martin Luther University Halle-Wittenberg). “It’s about time that soil conservation policies consider the protection of soil organisms and ecosystem functions more than just for food production and other productive systems. Soil biodiversity monitoring and conservation can support the achievement and tracking of many sustainability goals, targeting areas such as climate, food, and biodiversity protection.”

“Protection measures have so far mainly focused on life above ground, for example in the designation of protected areas,” says senior author Dr. Diana Wall from Colorado State University. However, since these do not necessarily benefit underground biodiversity, the specific needs of the biotic communities in the soil have to be taken into account.

In order to pinpoint which regions of the world are most in need of protection and which protective measures are most appropriate, sufficient information must be available on the condition and development of biodiversity in soils. Researchers in this field have launched the Soil BON monitoring network in order to remedy the current lack of essential soil data. “We want to shift the focus of conservation efforts onto biodiversity in soils. To do this, we will need to provide policymakers with the necessary information to support decision-making,” says senior author Professor Nico Eisenhauer, research group leader at iDiv and Leipzig University. “Soil BON will be a key tool in our efforts to deliver the necessary data on soil biodiversity,” says Professor Matthias Rillig from the Institute of Biology at Freie Universität Berlin.

The purpose of Soil BON is to help gather equivalent and comprehensive soil data over extended periods of time. An internationally recognized standard that sets out what is to be recorded and the methods used to this end is paramount. The researchers have therefore proposed a holistic system to meet this requirement called Essential Biodiversity Variables (EBVs). EBVs are key parameters for measuring biodiversity. The concept includes criteria such as soil respiration, nutrient turnover, and genetic diversity. Indicators are derived from the EBVs, which then serve as a basis for soil status evaluation and subsequent decisions regarding the level and type of protection necessary for the soils.

According to the researchers, the proposed monitoring and indicator system will enable the worldwide condition of soils and their capacity to function to be recorded and monitored efficiently in the long term. “It is high time we improve our understanding of what goes on beneath our feet. This harmonized, high-quality data on soil biodiversity will be essential to test if nature conservation measures are sufficient, and could alert us to areas where we need to do more to protect biodiversity in soils,” says Professor Rillig.