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BEFORE THE OREGON BOARD OF FORESTRY
Statement of Mary Scurlock
Oregon Stream Protection Coalition
25 April 2018
Agenda Item 7: State Forest Management Plan
I am Mary Scurlock for the Oregon Stream Protection Coalition, a federation of twenty-five
conservation and fishing organizations supporting my advocacy to protect freshwater
ecosystems on Oregon’s nonfederal forest landscape.
I appreciate the Board’s thoughtful conversation around state forests today, and especially
your commitment to consideration of best available science to develop a durable management
plan that integrates the state’s goals for management of state forests’ valuable natural
resources and merits federal assurances under the Endangered Species Act.
Today I’d like to highlight significant recent findings about the relationship between forest
management and water flows that were the subject of an April 4 conference at the Pacific
Northwest Research Station in Corvallis entitled “Summer Low Flows in Western Oregon:
Processes, Trends, Uncertainties, and Forest Management.” The meeting was organized by
the Research Station, BLM, Weyerhaeuser Company and NCASI.
Tim Perry and Julia Jones of OSU published a study in 2016 that analyzed long-term paired
watershed data from experimental forests in Oregon. (Enclosed). The results extend and
sharpen previous analyses of post-logging effects on instream flow, concluding that after an
initial 10-15 year period of increased baseflows (late spring, summer and early fall), stream
flows are reduced by about 50% for a period lasting from 15 to at least 50 years. These
persistent low flows resulted where more than half the catchment area was logged – that is,
where less than half the watershed area remained in mature and old growth forest. The
ultimate timeframe for return to the higher base flow conditions observed before logging
remains unknown. It could be 60 years, or it could be 120, or more.
The hydrologic explanation for low flow depletion appears to be increased evapotranspiration
in second-growth forests due to greatly reduced water use efficiency and also, possibly,
increased physical evaporation (from soil, or from condensation on the outside of foliage,
etc.) in second-growth compared to mature and old growth conifer forests. The relatively
consistent and sustained low flow deficits among the study basins supports the applicability of
the results to logged watersheds across the Pacific Northwest, particularly where Douglas fir
is the dominant tree species.
A key take home message from the conference is that not only are the findings of the Perry
and Jones (2017) study broadly relevant to forest managers, but not one of the paper’s
findings or speculative discussion points were scientifically challenged at the meeting. Given
the credibility of this new science, this Board will have to grapple with its implications in a
variety of policy forums, including in state forest planning in basins where ODF is majority
owner such as the Trask, Kilchis, and Wilson rivers.
Other important take-aways from the conference are:
• It’s not just small headwater streams that are affected by persistent low flows; in
most cases streamflow decreases will aggregate to reduce flows downstream;
• We can’t prevent or even mitigate for flow depletion with riparian buffers
• Modified harvest practices like thinning or staggered short-rotation clearcuts are
also likely to be ineffective at reducing or mitigating depletion of streamflows;
• Past widely-cited textbook claims and assumptions in agency plans and
assessments of a 10-15 year “hydrologic recovery” after clearcut logging are
fundamentally wrong and do not represent current science.
We strongly support more research to better predict, understand and prevent the low flow
effect, but available science is indisputable that the effect real. The management implications
seem clear: if we truly want to conserve water and the species and human communities that
depend on it for life in an era of climate change, more short-rotation logging is not in the
cards. More older forests and longer-rotation forestry will be needed to protect and stabilize
water flows.
References
Jones , J.A., and D.A. Post. 2004. Seasonal and successional streamflow response to forest
cutting and regrowth in the northwest and eastern United States. Water Resources
Research 40:W05203. doi:10.1029/2003WR002952. Online at:
http://andrewsforest.oregonstate.edu/pubs/pdf/pub2787.pdf
Perry, T.D., and J.A. Jones. 2016. Summer streamflow deficits from regenerating Douglas-fir
forest in the Pacific Northwest, USA. Ecohydrology 2016:1-13.
DOI10.1002/eco.1790. (Enclosed)
Luce, C. H., & Holden, Z. A. 2009. Declining annual streamflow distributions in thePacific
Northwest United States, 1948–2006. Geophysical Research Letters 36(16): L16401.
Online at: https://www.fs.fed.us/rm/pubs_other/rmrs_2009_luce_c001.pdf