This article first appeared in the April 2021 issue of the Forestry Source: Vol. 26 - No 4.
Forest carbon management has been a hot topic lately. Foresters, biometricians, and policymakers are increasingly engaged in the design and implementation of programs to measure, monitor, and verify carbon sequestration. These programs reflect a common goal shared by all whose life and work is influenced by our changing climate: to reduce the impact of atmospheric carbon emissions.
Recently, a fellow forester reached out for advice on how to consider designing a field sample for carbon estimation. Jason Holmes is an Inventory & Analysis Forester with Bayfield County Forestry & Parks in Bayfield County, Wisconsin. Bayfield County Forestry & Parks is responsible for management of 175,000 acres of forests in northern Wisconsin, including county forests, campgrounds, and parks. Their mission includes a focus on current and future generations - prompting Jason and his team to begin thinking about measuring, monitoring, and perhaps monetizing the forest carbon on their lands.
His question was:
"Help! Is there a difference between plots sampling for forest carbon and plots sampling for traditional CFI (continuous forest inventory)? I've spent a good portion of the last 3 years collecting CFI data, basically FIA (Forest Inventory and Analysis) P2 plots, and I'd like to think that I'm sampling the right variables for carbon estimation. What might I be missing?
Jason and I exchanged a few emails at the beginning of the year, and I’m expanding on that conversation and adding some more thoughts in this column.
There are two different ways to approach this type of decision- accurate quantification of the variables of interest, and measuring the right things in the right way for a carbon program. While they are closely related, they aren’t completely linked, so it’s worth thinking about the question from both sides.
- How can you design a sample to measure and monitor forest carbon?
- What measurements are necessary to enroll property in a certified carbon project?
To answer question 1, we can turn to a wealth of information already available to practitioners, by following the example of the USFS Forest Inventory and Analysis program. The FIA sample design includes a protocol to measure understory and overstory information, and provides a framework for working up carbon metrics for individual stems. Currently this is done by estimating the total above ground biomass through the estimated amount of biomass in components of each stems (bark, below-ground biomass, above ground biomass, etc). In addition, the USFS supports ongoing research in improving the processes for estimating these variables and components.
Jason shared that, using FIA as a model, Bayfield County Forestry & Parks has established a Continuous Forest Inventory system that is comprehensive and detailed. He told me, “ the normal suspects get measured – DBH, spp, dead/alive, growing stock/rough cull/rotten cull, rot %, tree grade, total height, compacted crown ratio, relative position in the general canopy, damage or diseases.”
This is a wealth of information - for monitoring and tracing forest change, understanding current and future possible forest conditions, and estimating and summarizing many variables of interest - volume, value, potential for wildlife habitat and non-timber products, and estimating and tracking the standing carbon in the forest.
One of the immediate questions becomes, what’s included in your analysis? What carbon are you tracking, and what pools of carbon are most influenced by the decisions you make now or in the future? Outside of highly focused, census-based research endeavors, there is always a tradeoff between sampling design and detailed measurements. Rarely do we have the ability to measure seedlings, saplings, and overstory stems with as much precision as we’d like - that’s why we sample! It’s important to understand the design of your sample and how to incorporate this into your summaries and interpretation of the information collected. Without careful consideration, we end up overinvesting, and collecting an amount of data to reach a precision that’s more than necessary to guide decision-making.
For Jason and his team in Wisconsin? They’ve been collecting data for several years. They are monitoring all the forest attributes of interest for their team, and designing a sample and a field protocol to closely follow the approaches for which the FIA protocols for estimating carbon have been designed. There’s nothing magic about carbon - estimating the resource in terms of living or total carbon is one of many ways to quantify what forests provide, and a robust data collection process allows you to estimate carbon, quantify uncertainties, and make decisions just like any other.
But what about measuring the carbon in leaf detritus, or below-ground biomass, or coarse woody debris?
I’d go with “If you can see why you want to measure this, find a good example of practitioners doing this, and follow suit!” But for most lifecycle and systemic analyses, defining the boundaries of the analyses becomes a key part of the work -- and in the world of forest carbon, practicalities generally win out. It’s very difficult to measure and monitor below-ground biomass, so it’s generally left out, or estimated through a protocol of ratios and heuristics such as the Component Ratio Method. It’s easy to get distracted by certain aspects of the measurement protocol and lose the big picture - how are these carbon sinks or stores affected by changeable behavior?
“How do I measure forest carbon” is of course, a very important question. Where the rubber meets the road is in the second part of this problem - “What measurements are necessary to enroll a property in a certified carbon project?” The answer lies in understanding how carbon methodologies are established and how projects are enrolled.
Certified carbon methodologies include information and requirements for measuring and monitoring carbon for the duration of the project. Different methodologies can have different requirements for field measurements. In some cases, the process is entirely based on field mensuration, and under other protocols and methodologies, remote sensing-based or remote-sensing-assisted processes are accepted.
There’s also a question of time frame - under some programs, preliminary data can be less precise, with more intensive measurement protocols followed once properties are enrolled. The general framework is that the methodology lays out what must be understood with appropriate precision at the appropriate time, with a protocol and project certified under that methodology meeting those requirements.
So what about Jason’s question?
Jason’s initial question was whether he and his team had been measuring enough about their forests to explore enrollment of those forests into forest carbon programs. They have certainly been measuring enough to understand their current activities and carbon stocks.
But more relevantly, the process of enrolling a property into a carbon project generally includes additional data collection - and the companies and organizations that work to help landowners and managers enroll their acres are skilled in making this happen. Whether you are interested in exploring a short-term or longer-term contract for carbon sequestration or improved forest management on your property, the data you have or have not collected isn’t going to keep you from moving forward. Qualification for enrollment and the costs and benefits associated, are more a function of the history, structure, management, and type of commitment you’re able to make as a landowner or manager. In many cases, having some practice thinking about the various priorities you have for your land--for example, thinking about how your economic expectations relate to your aesthetic expectations for your property--is going to be more important preparation for participation than data collection.
The potential of forests - both working forests and preserved and conserved land - to sequester carbon is an immense benefit to our current and future generations. As foresters, our responsibility is broad. First, we should understand how to accurately and appropriately measure this resource. Secondly, we should understand how to integrate our stewardship of this carbon resource along with values- timber, aesthetics, mitigating fire risk, and everything else our planet and our society gains from growing forests.