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The Stunning Ways Driftwood Builds Landscapes

Lines of spruce trees that grew along decaying driftwood piles mark the locations of past shorelines for thousands of years. (Photo by Natalie Kramer Anderson, Aug 2014)
Lines of spruce trees that grew along decaying driftwood piles mark the locations of past shorelines for thousands of years. (Photo by Natalie Kramer Anderson, Aug 2014)

By Natalie Kramer Anderson

I study driftwood in rivers. I have traveled to rivers and creeks in Canada, the United States, Colombia, Chile, Honduras, Mexico, Peru, Italy, and Switzerland noting the abundance, or lack thereof, of streamside wood. For the past few years, partly funded by the National Geographic Committee for Research and Exploration, I have intensively studied the transport and impacts of large amounts of driftwood on big rivers and lakes in Northern Canada, and I just published a paper on what we found.

Funded by the National Geographic Society

When I speak to people about my research they always ask, “Why driftwood?” For many it seems an odd thing to study because driftwood (in rivers) isn’t something that most people notice. In fact, several perception studies have shown that throughout the world most people actually relate dead wood along stream channels with the need to restore or clean up the river channel.

Driftwood facilitates the formation of forested island bars. Liard River, British Columbia, Canada. (Photo by Natalie Kramer Anderson, Sept 2013)
Driftwood facilitates the formation of forested island bars. Liard River, British Columbia, Canada. (Photo by Natalie Kramer Anderson, Sept 2013)

In reality, driftwood is a very important component of all natural waterscapes.

Driftwood alters the physical form of banks and ­­­­­­­­­shorelines, creating patchwork landscapes that support higher levels of biodiversity and ecosystem functioning than in the absence of wood.

Driftwood is an important line of defense along coastal beaches against erosion by waves, which is especially important as sea levels rise.

World-wide dispersal of organisms is often attributed to rafting on wood across oceans, and sunken wood in the deep ocean supports webs of life that would otherwise not exist in such an extreme environment with no light source to fuel plant growth.

Invertebrate light trapping on drift piles on large gravel bars. Free flowing Marañón River, Peru. (Photo by Natalie Kramer Anderson, July 2015)
Invertebrate light trapping on drift piles on large gravel bars. Free flowing Marañón River, Peru. (Photo by Natalie Kramer Anderson, July 2015)

There is a striking difference in amount of driftwood and habitat quality when comparing river corridors with and without intensive development, such as dams and deforestation for agriculture.

In Colombia, South America, driftwood lines the banks along rivers, such as the Samaná, that flow through jungles left intact during guerilla warfare and is absent in nearby deforested and heavily grazed catchments. The free-flowing Rio Marañón in Peru is located in the high Andes. Despite draining a canyon with sparse vegetation, large driftwood piles accumulate on top of mid-stream gravel bars in wider and flatter sections. Both the Rio Samaná and Rio Marañón have proposed large hydropower projects that will be built within the next decade.

A river wide raft in a side channel to the Slave River, NWT, Canada. This same raft was noted in the journals of Alexander Mackenzie circa 1789 during his quest to find a route to the Western Ocean through Canada. The trees to the back of the raft are growing out of driftwood. (Photo by Natalie Kramer Anderson, Aug 2015)
A river wide raft in a side channel to the Slave River, NWT, Canada. This same raft was noted in the journals of Alexander Mackenzie circa 1789 during his quest to find a route to the Western Ocean through Canada. The trees to the back of the raft are growing out of driftwood. (Photo by Natalie Kramer Anderson, Aug 2015)
Overview of the wood in the middle front of the Slave River log raft. Natalie Kramer Anderson and Cole Conger pictured. (Photo by Natalie Kramer Anderson via UAV, Aug 2015)
Overview of the wood in the middle front of the Slave River log raft. Natalie Kramer Anderson and Cole Conger pictured. (Photo by Natalie Kramer Anderson via UAV, Aug 2015)

European rivers generally lack wood due to a long history of streamside cultivation, but many rivers are currently undergoing re-forestation due to de-settlement during and after WWII. River managers are noticing an increase downed wood, and researchers are studying the benefits to the ecology and the problems with deposition against bridge piers and other in stream structures.

In the Mississippi basin, United States, historical accounts from European settlers describe stream wood accumulations that were so massively impressive in size that it verges on unfathomable to those of us who visit the river today. One observer described a river wide raft on the Red River in Louisiana circa 1928 as:

“…not standing still, but is gradually progressing upwards, like a destroying angel, spreading desolation over a most lovely country” (D. Joseph Paxton, 1828)

Here I am collecting wood measurements on the Slave River, NWT, Canada. (Photo by Leif Anderson, July 2013)
Here I am collecting wood measurements on the Slave River, NWT, Canada. (Photo by Leif Anderson, July 2013)
Vegetation and sediment fill in the back of the Slave River log raft. (Photo by Natalie Kramer Anderson, Aug 2015)
Vegetation and sediment fill in the back of the Slave River log raft. (Photo by Natalie Kramer Anderson, Aug 2015)
A wood flood on the Slave River, NWT, Canada deposited this log jam in 2011; it was completely gone by 2013. This illustrates the transient and mobile nature of large wood in a mostly intact large river basin. There are plans to dam the both the Slave River and its main tributary, the Peace River. (Photo by Natalie Kramer Anderson, Aug 2011)
A wood flood on the Slave River, NWT, Canada deposited this log jam in 2011; it was completely gone by 2013. This illustrates the transient and mobile nature of large wood in a mostly intact large river basin. There are plans to dam the both the Slave River and its main tributary, the Peace River. (Photo by Natalie Kramer Anderson, Aug 2011)

Of course, the spreading desolation point is a matter of cultural opinion.

In rivers draining the mostly undammed Mackenzie basin in Canada, river rafts and landscape features associated with wood are abundant and reflect conditions that were likely more common world-wide for the last 10,000 years up to about 200 years ago. The impacts of large amounts of driftwood on waterscapes—ecological and physical—is absolutely stunning both in scale and in aesthetics which is best conveyed through imagery.  Here are a few of my favorite photos from my latest field excursions to the Slave River and Great Slave Lake in the Northwest Territories, Canada.

Wood from the Slave River is deposited into the Great Slave Lake where it is permanently stored along the shorelines. The wood piles facilitate sedimentation and vegetation and are a crucial element shaping shoreline morphology and creating a patchy landscape with diverse habitats. (Photo by Natalie Kramer Anderson, Aug 2014)
Wood from the Slave River is deposited into the Great Slave Lake where it is permanently stored along the shorelines. The wood piles facilitate sedimentation and vegetation and are a crucial element shaping shoreline morphology and creating a patchy landscape with diverse habitats. (Photo by Natalie Kramer Anderson, Aug 2014)
Spruce seedlings preferentially germinate in decaying logs along the shore. (Photo by Natalie Kramer Anderson, July 2013)
Spruce seedlings preferentially germinate in decaying logs along the shore. (Photo by Natalie Kramer Anderson, July 2013)
Reeds and grasses capture floating mats of wood and sediment delivered from the Slave River. Just under the surface, logs are buried into sediment meters thick. Ellen Wohl pictured. (Photo by Natalie Kramer Anderson, July 2013)
Reeds and grasses capture floating mats of wood and sediment delivered from the Slave River. Just under the surface, logs are buried into sediment meters thick. Ellen Wohl pictured. (Photo by Natalie Kramer Anderson, July 2013)
Not just large wood, but wood pulp is delivered to the Lake and is deposited in wind protected areas. Wood pulp is a readily available and nutrient rich resource for ecosystems. (Photo by Natalie Kramer Anderson, Aug 2014)
Not just large wood, but wood pulp is delivered to the Lake and is deposited in wind protected areas. Wood pulp is a readily available and nutrient rich resource for ecosystems. (Photo by Natalie Kramer Anderson, Aug 2014)
This is one of my favorite photos from the Slave River outer Delta that really shows significance of driftwood on large scales. Note the formation of a new outer bar of driftwood which protects the mainland from waves. Also note the line of trees fronted by almost completely vegetated decayed wood that marks the position of a previous shoreline. In the background, a large bay is becoming enclosed by vegetated driftwood bars. Offshore standing water bodies are important sites for carbon capture from the atmosphere. (Photo by Natalie Kramer Anderson, Aug 2014)
This is one of my favorite photos from the Slave River outer Delta that really shows significance of driftwood on large scales. Note the formation of a new outer bar of driftwood which protects the mainland from waves. Also note the line of trees fronted by almost completely vegetated decayed wood that marks the position of a previous shoreline. In the background, a large bay is becoming enclosed by vegetated driftwood bars. Offshore standing water bodies are important sites for carbon capture from the atmosphere. (Photo by Natalie Kramer Anderson, Aug 2014)

As the world’s last free flowing rivers are rapidly dammed for hydropower, I wonder: how will diminishing transport of driftwood impact the biodiversity of river corridors and marine environments? How much more at risk are wood-depleted coastlines from erosion associated with sea level rise and extreme weather? And, what impact will wood depletion have on freshwater and marine fisheries?

Natalie Kramer Anderson – Wood Research short from Anderson Productions on Vimeo.

My work has been funded by the National Geographic Committee for Research and Exploration, the Geological Society of America, Chuck Blyth, and the Warner College of Natural Resources, Colorado State University.

Suddenly hooked on driftwood? We’ve got you covered: Additional Reading.

 

Comments

  1. Cynthia
    United States
    August 30, 2015, 8:13 am

    Fascinating! Wonderful research.

  2. James Burke
    France
    August 30, 2015, 7:06 am

    Fascinating! Our self-repairing earth, if given a chance.
    Thank you

  3. Kirsten Murphy
    CBC North Interview Request
    August 28, 2015, 6:06 pm

    Hello Natalie,
    I am a producer in Yellowknife.
    We are interested in finding out more about your work.
    Are you reachable by phone?

    Kirsten
    867-920-5423
    867-444-3236

  4. Jay Merrill
    Fort Collins, CO
    August 27, 2015, 10:30 am

    Natalie, this is a wonderful article and amazing video. Hope you are doing well.