The science is in!

The open-access, scientific journal Diversity published the paper, Siskiyou Crest Ecoregion Conservation Assessment for the Klamath-Siskiyou Ecoregion and Proposed Siskiyou Crest Climate Refuge, Southwestern Oregon and Northern California, USA. This Ecosystem Conservation Assessment (ECA) provides an in-depth look at the values of the Siskiyou Crest region, charts a path towards protection targets of 30% and 50% of the landscape, models future climate scenarios, identifies climate refugia attributes, examines wildfire severity across the landscape, and identifies high-value connectivity corridors for focal species like the northern spotted owl and Pacific fisher in the Siskiyou Crest region.

This groundbreaking scientific study directly focuses on the Siskiyou Crest and compares the values of the Siskiyou Crest with those of the larger Klamath-Siskiyou Ecoregion. It also identifies a need for additional habitat protections and management focused on biodiversity and the maintenance of biological processes, old-growth forests and watershed values.

As a companion to the peer-reviewed Assessment, there is a general audience-friendly Atlas that requires less technical and scientific background. It offers summaries of all the most important ECA findings and is a great resource in itself.

According to the ECA, “The KSE is considered a “center of floristic diversity and narrow endemism” [9]. The ecoregion supports a continental maximum of conifer species [12] along with exceptional mollusk (Mollusca); butterfly (Lepidoptera); bee (Apidae) [13]; and amphibian richness and endemism ([10,14] for reviews). Notably, the KSE has the most species-rich herpetofauna of any similarly sized mountain range in the Pacific Northwest, in part due to eight endemic species [15]. Plant endemism on ultramafic substrates is exceptional, promoted by the combination of extensive serpentine areas and a moderate inland to coastal climate [16].

The KSE also has presumed refugia properties related to its moderate climate [8,10,17] and the lack of volcanic activity and glaciation events. In particular, old forests on north- facing slopes [18] have been proposed as potential refugia in this ecoregion presumably because of favorable microclimatic properties (cool, wet). The primarily east–west running, high-elevation Siskiyou Crest Subregion (SCS) within the KSE is also noted for its high biodiversity and forest carbon importance that is greatest in older forests [19], along with its land-bridge functions connecting the Cascade and Coast ranges [18].”

The paper found that the Siskiyou Crest subrange had more complex forests than the Sierra Nevada and Cascade Mountains, and that it “stands out as having a high concentration” of old-growth forest. Although the Siskiyou Crest only comprises 14.5% of the Klamath-Siskiyou Ecoregion, it contains 18.8% of the forests over 80 years old and 21.8% of the forests over 200 years old. Of particular importance is the level of “persisted” old-growth both in the larger Klamath-Siskiyou Mountains and Siskiyou Crest subrange that has burned at least once since 1985, yet remains in an old-growth condition. Higher levels of “persisted” old-growth were found in unmanaged forests of the Siskiyou Crest, including Wilderness Areas and Roadless Areas, than in the managed landscape where logging and commercial fuel treatments are more prevalent.

With this concentration of older forests in the Siskiyou Crest region, habitat for the northern spotted owl and Pacific fisher is particularly abundant, but at very low levels of protection— older forests are only protected on 10% of the landscape. Notably, “the Siskiyou Crest may function as fisher refugia due to high proportions of connectivity habitat.”

“Additionally, many older forests in this fire-prone ecoregion have escaped recurring severe fires by chance or because of their cooler/wetter microclimates acting as long- standing refugia (persistence) for focal species like the Northern Spotted Owl and Pacific fisher.”

Downscaled climate modeling showed that the Siskiyou Crest, “is likely to retain moister, cooler conditions for longer periods” than the surrounding landscape, making it important climate refugia. The ECA also demonstrates “the key potential refugia properties of IRAs [Inventoried Roadless Areas], old forests and select LWCs [Lands with Wilderness Characteristics] that tend to burn at lower severities (as in [23,40]), and intact watersheds for focal species connectivity (e.g., Pacific fisher). If protected, these areas offer the best hope for extending the “hang time” for plants and wildlife to adapt while providing invaluable ecosystem services (e.g., clean water, clean air, recreation, fire refugia) to communities.”

Unfortunately, much of the area is underprotected, and even if habitat protections were increased for Inventoried Roadless Areas on Forest Service lands and Lands with Wilderness Characteristic on BLM lands, protections levels would approach 25%, remaining deficient in the 30X30 protection target. This points to the need to protect the most intact portions of the landscape such as Inventoried Roadless Areas and Lands with Wilderness Characteristics, plus citizen-identified roadless areas, old-growth forests, and biodiversity hotspots. Only this would achieve the lowest levels of the 30X30 protection target.

The ECA also mapped and analyzed the contemporary fire regime for the region and found that wildland habitats in Wilderness Areas, Inventoried Roadless Areas, and Lands with Wilderness Characteristics areas burned with lower levels of wildfire severity fire than the “managed areas” adjacent to them. This was found across a regional scale from 1985-2023 for all large fires that burned in the Siskiyou Crest region.

The ECA researched the relationship between BLM and Forest Service fuel treatments and the built environment. That analysis found that “most fuel treatments… are far removed from the built environment” and are either not designed directly to protect communities from wildfire impacts, or will be ineffective at doing so. The ECA calls for “a more strategic focus on community protection within a narrow defensible space area around structures themselves [88,89] along with a redirect of wildfire spending to home hardening.”

Overall, the study points to a region of globally significant biodiversity, “under increased land-use and climate stressors.” It also verifies the importance of the Siskiyou Crest in maintaining habitat connectivity and climate refugia on a regional scale. The Siskiyou Crest and larger Klamath-Siskiyou Ecoregion “can contribute to global targets through increased local conservation that effectively moves the ecoregion and subregion into the upper protection levels while restoring degraded portions of the ecoregion. Our results span multiple ecoregions facing mounting pressures that overall would benefit from increased protection of locally proposed protected areas and refugia.”

The science is clear: the Siskiyou Crest deserves habitat protection for a broad spectrum of reasons, many of which were documented in this groundbreaking peer-reviewed scientific paper. The ECA identifies habitat connectivity, globally significant biodiversity, a particularly high concentration of old-growth forests, and important climate and fire refugia as values to protect. We could not agree more!