From Dead Wood to Living Landscape

While "dynamic landscapes" are popular concepts in academic settings, in reality most designers and clients are uncomfortable working with living and changing matter in the landscape, gravitating to concrete and stone that can be fixed with minimal weathering. As the plant material in our landscapes grows, moves, and changes more predictably based on known biology and environmental factors, the idea that we might install an engineered structure designed for disturbance and decay is difficult to comprehend and more difficult to justify, but increasingly important. Ecologists Berg, Streaker, and Streb with Biohabitats describe such a system built in a Maryland forest, using techniques that are gaining favor in application: locally harvested timber-made structures that mimic the dam building of beavers and natural tree-fall in the forest by creating hydrological barriers across the landscape. In recent years, much interest has developed around the engineering work of beavers and their role in the restoration of hydrological landscapes. Among the many brilliant scientists and writers contributing to this work, two stand out, 1) Glynnis Hood, a Canadian ecologist who documents the recovery of the North American beaver in her book "The Beaver Manifesto" (2011) and their potential role in mitigating and climate change, and 2) Ben Goldfarb, who profiles the "Beaver Believer" movement (2019), interviewing a diverse range of advocates, scientists and land managers working to return the beaver to their historic habitat. I have also studied beaver landscapes across the Western Slope of the Rocky Mountains (Passmore 2019), visiting around 30 beaver wetlands in New Mexico, Colorado, Utah and Idaho, to learn from them about bringing water back to arid landscapes.

Like beaver dams, these wood structures designed by Biohabitats support increased water retention, ecosystem enhancements and broader floodplain health by creating micro-conditions where blockages can occur. By mimicking what would have been a messier, more complex forest floor condition pre-development, they are engaging with the aliveness of the forest and the wood itself. In this, they connect an engineered solution directly to the character and materiality of this coastal forested floodplain, where a traditional rock dam or weir would be foreign. Although the wood structures will surely transform, break, and rot, it is this lightness, softness, and weakness of wood that makes it so effective. Sourced from the immediate site, it can be transported easily and fabricated and installed using low-tech and cost-effective methods. This work could be done in conjunction with forest thinning initiatives or maintenance programs that address broader forest health. Where I work in the West, similar beaver dam analog systems ("post-assisted log structures") have been essential to post-fire landscapes to mitigate erosion and the loss of sediments and nutrients (Shahverdian et al. 2019).

Biohabitat's approach to using raw timber will be most effective in forested contexts, and therefore may need to be adapted depending on the surrounding landscape. Beaver also build with what is available nearby; along Western streams I observed dams built with willow (Salix spp.), cottonwood/aspen (Populus spp.) and even sagebrush (Artemisia tridentata). Conifer species such as spruce or pine are available, but less palatable to beaver. These western woods tend to be softer, more porous and pliant; they can achieve strength in numbers but may decay quickly. Biohabitats' structures, if built using these materials, would likely require more maintenance or have a shorter life span. If regularly maintained, like beaver dams, I would expect that this system would last for decades, but ultimately depends on how "flashy" or prone the watershed is to large destructive flash flood events.

Biohabitats' system in its context is remarkable because it also has the potential to regenerate independently, though chaotically. As the forest continues to shed branches and detritus, new wood will feed the dams as it is caught by the structures. Over time the landscape will take on a life of its own, a truly living system. Do we accept this uncertainty, develop models for prediction, or create a stewardship program to control the outcome? It is the unpredictability and maintenance required that may make it difficult to convince a municipality or private client to pay for this type...