The value of monitoring soil

Finally, a soil MRV review paper we didn’t have to write.

by Jane Zelikova and Elizabeth Reali

How we think about and measure soil carbon

Though there is renewed interest in soil health and carbon today, the concept of soil “quality” or “health” has been around for a long time. Fifty years ago, “soil health” was shorthand for maximizing crop yields. Over time, our objectives have shifted, along with the methods we use to assess soil health and how we turn those data around into management decisions. Today, the definition of soil health has expanded to consider the role that soils can play in supporting ecosystem services and mitigating climate change.

Source: Carbon180
Pete Smith et al. explore common approaches to soil carbon quantification, along with their benefits and challenges. Source: Carbon180

The challenges ahead

Methods

Though the world is finally turning overdue attention to carbon removal and the untapped potential for carbon sequestration in agricultural soils, the methods that underpin our ability to do so reliably and cost-effectively are lagging behind. We need tools that allow us to measure SOC non-destructively (as in, without having to dig a hole) and model how different agricultural practices affect soil carbon. The dream would be to have the ability to scan a sample in Montana, then instantly add it to a global library of soil samples, where it can be referenced across a database to help improve future predictions of soil SOC in similar contexts.

Geographic bias

In order to harness the power of soils to draw down atmospheric carbon, we need to expand soil carbon monitoring across the globe. Today, many regions lack both long-term monitoring and infrastructure in order to adequately quantify and track soil carbon stocks changes across time. And long-term experiments are also limited in geographic scope, restricting the broad applicability of the results to mostly temperate ecosystems. Ramping up capacity and expanding soil monitoring across the globe is critical.

Variation

As soil scientist Tony Hartshorn (Montana State University) likes to say, soils are sneaky — you can walk a few meters and find yourself on a different soil type, with inherently different properties and soil carbon sequestration capacities. That means we need to collect soil samples from a lot of spots to get a better sense of how soil carbon inherently varies and how different management approaches affect it.

Impatience

Soil C gains can be slow and small enough from one year to the next to be undetectable. That means we need to think about MRV protocols that take the speed of carbon accrual into consideration, and payment schemes that support farmers through the 3–5 years it takes for soil carbon to accumulate at measurable rates.

Diversity of stakeholders

Many groups rely on soil MRV today, and many more groups will need to in the future as natural climate solutions become more mainstream. The groups that need to accurately measure and track soil carbon include:

  • Businesses that rely on agricultural products and have made climate commitments, including building soil health and maximizing soil carbon sequestration
  • Government entities (at the local, regional, national, and international scales) that have expressed greenhouse emission reductions goals that include carbon drawdown by plants and soil or that regulate emissions
  • Scientists who are improving modeling approaches and developing new tools for soil carbon measurement and verification
  • Policymakers developing incentive structures that rely on trusted and accurate measurement of soil carbon
  • Philanthropies that are building strategies around carbon removal and need to understand both the challenges and opportunities of soil carbon sequestration.

So, what comes next?

We have a long way to go to address the challenges in front of us and make the most of soil carbon sequestration’s potential. Luckily, we’re not starting from scratch. We know how to measure soil organic carbon, we have modeling platforms that are getting better and better every day, and we have a growing community of farmers and ranches who are excited to test out new agricultural practices and track soil changes.

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