Land, Water and People: In praise of the riparian life zone

The willows were almost impenetrable. Thick and as tall as me, I had to spread the upper branches while stepping on the lower stems to slowly work through the jungle. I knew I was about halfway through when I reached a small, gurgling creek.

Ten minutes earlier, I had been standing in an alpine meadow near the headwaters of East Willow Creek (well named!). I wanted to cross over to the other side of the valley and the 100 foot wide green, sinuous ribbon of willows that followed the creek didn’t look like that big of a deal to wade through.

The strip of willows that followed the creek is known as a riparian zone. Riparian life zones are water-loving, vegetated areas along rivers and streams. They make up less than 2 percent of the land base in the West and close to six percent on the Rio Grande National Forest, but are used, at least part time, by up to 80 percent of the wildlife.

Riparian zones in our middle and high elevations are usually dominated by willows, sedges and a variety of herbaceous plants. When willows are absent, small creeks can often be recognized from a distance by the white heartleaf bittercress that line their banks in June. Bluebells, larkspur, monkshood, rose crown, Parry’s primrose and, one of my faves, yellow monkey flowers may also join in.

Blue spruce trees thrive in riparian zones in the mid elevations and either share space or are replaced by cottonwood trees below 9,000 feet in elevation. Juniper trees will also sometimes mix in below cottonwoods.

The lush vegetation found in the riparian zone provides cooling shade for the creeks and rivers they line helping cold water insects and fish thrive. Leaves that fall into the water provide detritus, which is an important ingredient in the aquatic food web. Aquatic insects and other invertebrates feed on the dead leaves and, in turn, are fed upon by other insects, fish and even the bottom-waking, wing-swimming bird, American dipper.

Many of the insects found in creeks and rivers are there only in larval stages. They eventually emerge from the flowing water as flying insects and are consumed by birds and bats. Fly fishermen use wet flies to mimic insect larvae and dry flies that float on top of the water designed to look like flying insects.

A variety of small mammals thrive along riparian zones feeding on buds, seeds and fruit. The thick vegetation provides protective cover allowing them to safely disperse up and down the corridor allowing for the mixing of genetic material between populations.

Probably the best known mammal found in riparian zones is the beaver. Beavers are North America’s largest rodent and are famous for building stick dams and lodges on creeks in the mountains. The dams pool up water into ponds creating good fishing holes and increasing the amount of moisture that sinks into the ground. In rivers, where dam and lodge building can be challenging, beavers burrow into the banks to create their dens.

Riparian life zones are dynamic systems greatly influenced by the flows in the creeks and rivers they border. Periodic flooding saturates the floodplain and deposits sediment providing perfect conditions for willow, cottonwood and aspen seeds to germinate. Humans don’t always appreciate these occasional overflows, though, and sometimes build levees to contain the water to protect developments. This often has the unintended effect of narrowing the riparian vegetative zone as the trees and shrubs outside the levees disappear over time, because the lack of new sediment prevents reproduction by seed.

Riparian life zones have outsized importance in the dry west considering the small amount of space they occupy. But I wasn’t thinking about that importance as I struggled to get through the dense shrubbery near the headwaters of East Willow Creek. The next time I visited the area I took the long way around, which ended up being just as fast with a lot fewer scratches.

Mike Blakeman is the public affairs officer for the Rio Grande National Forest. He spends much of his free time scrambling around the mountains with a camera in his hand.


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