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When people think of timber harvest, Paul Bunyon in SCUBA gear is not the first image that comes to mind. However, in recent years, some companies have turned their attention toward the bounty of underwater timber that’s been hidden from sight for centuries. These logs may be described as river or lake reclaimed, deadheads, or sinkers. Boards created from sinker logs have gained desirability on the market because of the attractive color variation, durability, and perceived sustainable benefits.
Underwater Logging and the Environment
Boards cut from recovered logs are touted as sustainable or environmentally friendly, largely because they are not harvested from terrestrial forests. This insinuates terrestrial forestry is unsustainable and pulling logs from aquatic systems is a notch up on the illusive sustainability scale. In reality, there are costs and benefits to each method of timber harvest.
One method of harvesting sub-aquatic trees is to pull them up from lake or river bottoms, causing a disturbance of sediment that results in an increase of turbidity. Turbidity is a measure of water clarity calculated by how well light scatters throughout a liquid. High sediment suspension in the water leads to an increase in total suspended solids. When turbidity is increased at an unnatural rate, this creates problems on multiple levels within an ecosystem—blocking light for photosynthetic organisms, smothering egg nests, and inhibiting hunting abilities of aquatic animals, to name a few.
Highly specialized underwater harvester machinery reduces this impact by cutting the upright trees rather than pulling them up by their roots. There is also the incentive to reduce turbidity so the underwater cameras are able to function for the operators. Although the harvesters minimize turbidity impacts, there are other impacts to consider such as riparian effects from haul out sites and staging areas, as well as the consequences of removing structures in an aquatic ecosystem that have been in place for decades, sometimes centuries.
From the standpoint of steelhead, for example, the sinker log provides an important role in habitat contribution in a river system. Just like terrestrial forests, aquatic habitat can be enhanced with structural diversity. A log wedged into a river bottom provides shelter from the currents. The log changes the flow pattern of the river to create eddies that bring in food and washes away fine silts, allowing formation of gravel beds. These gravel beds are crucial for anadromous fish spawning, allowing a place for eggs and young fry to hatch and develop without immediately getting washed away to sea. Logs in creek systems are significant sources of habitat quality, and when most of these logs are removed from a system, it could have detrimental effects on fish populations, not to mention other countless riverine species and the geomorphology of the river itself.