Rethinking Forest Health: Growth to Drain and the Rise of Natural Mortality

By Steve Courtney, John Kelley, & Roy Anderson The Beck Group Consulting

Service Spotlight: Fiber Supply and Demand, Strategic Planning, Capital Project Planning, Biomass and Small Diameter Utilization

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Timber industry veterans are well acquainted with the Growth to Drain (G to D) ratio. It is a core sustainability metric that compares the annual volume of wood added through forest growth to the volume removed by harvest and natural mortality.

• A 1:1 ratio means forest inventories are stable: growth equals drain and standing timber volume stays constant over time.

• A 2:1 ratio indicates a net accumulation: twice as much wood is growing as is being removed.

• A 1:1.2 ratio signals decline: more volume is lost than gained each year. Sustained over time, this would deplete the forest.

While critics may assume that the timber industry aims to cut every tree within reach, the reality is that long-term economic viability of the forest products industry demands sustainable forestry practices. The industry depends on G to D ratios of 1:1 or better to ensure long-term raw material availability.

The Emerging Challenge: Natural Mortality Outpaces Harvest

But what happens if forests aren’t managed at all?

Increasingly, lack of forest management—and the resulting buildup of insect infestations, disease, wildfire, and ultimately, natural mortality—is proving more harmful than carefully planned timber harvesting. In short, insects, disease and wildfire have become far greater harms to forests than people with hard hats and chainsaws.

The Numbers Tell the Story

While recently using the US Forest Service’s Forest Inventory and Analysis database to analyze timber inventories and growth to drain ratios for a client, The Beck Group identified a lesser used metric that illustrates how natural mortality has overwhelmed timber harvesting as the cause of tree death on Federal lands. It is Mortality to Drain (M to D), and it compares natural tree mortality to mortality from timber harvesting.

As shown in the table below, the computed M to D ratios on US Forest Service lands in Oregon, Washington, California, and Idaho range from a low of 2.1 in Oregon to a high of 10.3 in Idaho. That means natural mortality is overwhelming timber harvest activity. In contrast, the M to D ratio on private lands in these states are all well under 1. This suggests private landowners are much more proactively managing their forests to stay ahead of natural mortality.

The good news—as shown in the same table—is that in all four states, the computed G to D ratios are still at or above 1. This means that forests are still gaining volume year over year for now. However, the warning signs are clear: If natural mortality continues to rise unchecked, it could tip the balance and lead to net annual loss of forests—without any increase in timber harvesting!

Table: Growth (G) to Drain (D) & Mortality (M) to Drain (D) Ratios

for all Ownership Categories in Oregon, Washington, California, and Idaho

Table displays G to D and M to D Computed Ratios.

A Picture Can Tell the Story Too

The diagram below illustrates the G to D and M to D concepts using a visual analogy. Growth is shown as water pouring into a cup labeled Standing Inventory, while Drain occurs through two outlets: one controlled faucet representing timber harvest (which channels volume to productive use), and one uncontrolled leak representing natural mortality. In many Federally managed forests, that leak has grown significantly—leading to Mortality-to-Drain ratios as high as 10:1. Left unchecked, the standing inventory on federal lands will decline significantly. This image helps clarify the imbalance and underscores why lack of management is now a more serious threat to forest health than active harvesting.

Analogy of drain occurring through two outlets: one controlled faucet representing timber harvest, and one uncontrolled leak representing natural mortality. Note: a 4:1 Mortality to Drain ratio is a likely average for all four states combined.

Addressing the Imbalance

To improve outcomes on Federal lands, it’s not enough to simply raise harvest targets. The mill, logging, and trucking operations needed to carry out increased harvesting options disappeared decades ago. They won’t return without support.

The recent announcement aiming for a 25% increase in Federal timber harvesting is promising, but implementation will fall flat unless there are:

• A skilled workforce to plan and administer the management activities.

• A skilled workforce to conduct the harvest.

• Viable manufacturing facilities to convert the logs and smaller diameter biomass into products.

• Infrastructure in place to support the entire supply chain.

This is where partnerships matter. Federal agencies must help rebuild forest economies by investing in forest-based businesses from harvesters to processors and empowering local communities to be part of the solution. We tip our hard hats to the US Forest Service, who recently announced $80 million in grants aimed at boosting wood innovation and forest resilience.

How The Beck Group Can Help

When Congress provides Federal land managers with the tools and resources to rebuild the West’s rural timber industry, The Beck Group is ready. We will be there to help existing and new clients plan and implement practical, profitable, and sustainable forest stewardship strategies. Email info@beckgroupconsulting.com, let us know who you are and what you’re looking for, and we’ll route you to the best possible consulting professional for the task.

Or if you prefer a more personal connection, pick up the phone. At (503) 684-3406, you can speak with a live person or ask that one call you back.

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The Beck Group, Inc.

Forest Products Planning and Consulting Services

Telephone (503) 684-3406

Email: info@beckgroupconsulting.com