Available here — thanks to AFRC’s newsletter for the link — abstract below.
AFRC’s take on the report is worth a read:
The report determined that wildfire remains the leading cause for older forest losses on federal lands, accounting for about 70 percent of all losses since 1993. Naturally, those losses have not occurred evenly across the range of the NWFP. The most significant losses occurred in the eastern Cascade Ranges of Washington and Oregon, and the Klamath provinces in Oregon and California. Those losses were partially offset by old forest recruitment through stand growth in the Oregon Coast Range, Olympic Peninsula, and western Cascade Range in Washington, where catastrophic wildfires have been less common.
Despite being a minor component of overall losses, it is important to understand precisely what “losses” refers to in the context of timber harvest. A likely assumption is that a loss of old forest from timber harvest is a function of a regeneration treatment (clearcut, shelterwood, etc.) However, the data in the report suggests otherwise. The graphs below illustrate old forest losses (black line) on top of disturbance intensity; note that the two datasets are not graphed across equivalent acreages on the y-axis. The data shows that some moderate intensity fire causes a loss of older forest, and some does not; the same applied to timber harvest. What is noticeable is the complete absence of high intensity timber disturbance–the kind that would result from regeneration harvest. Instead, nearly all the losses are a result of moderate timber harvest such as thinning or intermediate harvest to restore historic open forest conditions or to reduce the likelihood of high-intensity wildfire.
I’d add that LSOG harvesting virtually stopped in 1993 and shortly after, and that future large fires are likely to change the equation in a significant way.
LSOG = late-successional and old growth forests
Abstract
This is the fourth in a series of periodic monitoring reports on the status and trends of late-successional and old-growth (LSOG) forests since the implementation of the Northwest Forest Plan (NWFP) in 1994. The objective of this monitoring is to evaluate the success of the plan in reaching its desired amount and distribution of LSOG forest on federal lands within the range of the northern spotted owl (Strix occidentalis caurina) in the United States. We began our assessment in the years shortly preceding the NWFP, but primarily focused on how LSOG forests have changed as a result of disturbance and forest succession since 1993, the year of the assessment that led to the implementation of the NWFP. We developed an annual time series (1986–2017) of LSOG maps based on an “old-growth structure index” (OGSI) using two age thresholds: ≥80 and ≥200 years. These ages represent when forests commonly attain stand structure associated with late-successional forests (OGSI 80) and old-growth forests (OGSI 200) in this region.
Maps showed a slightly increasing trend in LSOG forests (OGSI 80) on federal lands with a 0.3-percent net gain between 1993 and 2017. Forest Inventory and Analysis plot data from two measurement/remeasurement periods (2000s and 2010s) were used to corroborate mapped estimates. For OGSI 80 and OGSI 200 forests, we estimated gross losses from wildfire at 6.2 and 6.9 percent, respectively; timber harvest losses at 1.9 and 2 percent, respectively; and loss from insects or other causes at 0.7 and 0.9 percent, respectively. This indicates that, at the NWFP scale, processes of forest succession compensated for losses. The NWFP anticipated a continued decline in LSOG forests for the first few decades until the rate of forest succession exceeds the rate of losses. Decadal gross losses of about 5 percent per decade from timber harvesting and wildfire (combined) were expected. Over the extent of the NWFP, observed losses from wildfire generally met expectations, but losses from timber harvesting were about one-third of what was anticipated. Results were consistent with expectations for OGSI 80 abundance, diversity, and connectivity outcomes for this period of time. For OGSI 200, these outcomes were slightly degraded. Given that we are only one quarter into a 100-year plan, nothing in these findings suggests that desired outcomes are unattainable over the next 75 years. However, observed increases in frequency and extent of large wildfires, and expected additional increases owing to climate change, provide reasons for concern.