Threats to the Dunes
Dunes Are Fragile
As sturdy as they seem, dune plants are especially sensitive to human disturbance. Walking or driving all-terrain vehicles on them easily damages fragile surface vegetation and causes roots to die off. Without plants, the sand is exposed to wind erosion which destabilizes the dunes.
When vegetation is disturbed, a blowout can form. Blowouts are U-shaped depressions of bare sand in a stabilized dune. They originate on the windward face of a dune and are formed by wind gouging out channels in exposed sand. They can change the shape of parallel dunes by carving deep indentations. Due to the shape, these are called parabolic dunes.
On the windward side of some of these dunes, blowouts may uncover the bleached trunks of trees still standing after being buried in the dry sand for hundreds of years. These “ghost forests” are silent testimonials to ancient forests buried by drifting sand long ago. This phenomenon is visible on the large parabolic dune behind North Beach Park, one mile north of the Dunes Preserve.
On the steep backslope of a dune, moving sand from blowouts can also bury forests. This is happening on the dune near the outdoor classroom where you can see trees half buried in the sand. From the Hartger Trail, you can see that the windward side of this dune has a blowout.
Historically, blowouts have been caused by natural disturbances like fires, windstorms, or plant diseases. However, in recent decades, human activities and disturbances have destroyed sand-anchoring vegetation and initiated blowouts. Off-road vehicles and human foot traffic are the major causes, but clearing of protective dune vegetation to build homes, driveways, and commercial buildings have also resulted in large-scale wind erosion in man-made blowouts. Continuous human disturbance has the potential for much more widespread destabilization because blowouts are not allowed to restabilize naturally.
Exotic and Invasive Species
Exotic species are plants or animals that are not native to an area. They can be brought in by different means, such as planting them for landscaping or ornamental purposes without realizing the potential harm they can do; additionally, plant seeds can travel from place to place through people, animals, or the wind. Seeds will catch onto clothing, shoes, or fur and will be deposited in new locations as people and animals move from one place to another. Animals that consume the seeds can disperse them through their droppings. These are all ways that exotic plants can find their way into habitats in which they do not belong.
At the dunes preserve some exotic plants can cause harm to the dune environment by crowding out or damaging native plants that are critical for dune stabilization and succession. When this happens, the exotic species become known as invasive. There are a handful of invasive plant species that have invaded the preserve, and although volunteers regularly work to remove them, it is a constant battle.
Spotted Knapweed – This purple flower likes dry soil and can form massive monocultures along roads and highways. When this happens, it looks like a sea of purple. Even though it looks pretty, it is toxic and kills surrounding native plants. When this plant is detected early, it can be easily removed and contained. Since it reproduces by seed, it is important to pull it out before the seed heads open (Late July). We hold many spotted knapweed removal events throughout the year. Come out and help preserve the native plant populations.
Honeysuckle – There are several species of invasive honeysuckle in Michigan. This plant can grow up to 20 feet high and nearly as wide. It was most likely planted as a decoration by early residents who were unaware of its destructive nature. This plant outcompetes native plants at the preserve and is taking over many of the forests especially along the Lindquist and Hendricks Trail.
Japanese Barberry - This shrub has oval, spoon shaped leaves that turn red in the fall and bright red egg-shaped berries. It has large spines that line the underside of its branches. Japanese Barberry can thrive in a range of soil conditions and in sun or deep shade, and was likely planted as a an ormanental plant. It can spread via seed or the branch tips, which are able to root once they contact the ground. Japanese Barberry can be found along the Lindquist Trail, and is a major concern due to its recent link with increased deer tick populations and potential to spread Lyme Disease.
Dalmatian Toadflax – This plant is starting to become a problem near the open dunes and interdunal wetlands at the preserve. This yellow flower resembles snapdragons and likely was planted as an ornamental plant. It has an extensive root system and thrives in poor quality soil. This flower easily outcompetes native plants and reproduces by seed or through underground shoots. Because of this and its large root system, this plant is difficult to manage once established.
Oregon Grape - This invasive species colonizes the dunes and replaces native vegetation. Its seeds are easily dispersed because the berries are consumed by birds and mammals. When the shrubs have become well-established, they are nearly impossible to pull by hand. A highly branched root system allows Oregon Grape to firmly anchor itself into the sand.
Hemlock Woolly Adelgid - These are invasive insects that only effect Hemlock trees. They extract nutrients from the trees which results in damage to needles, shoots, and branches. Left untreated, Hemlock Woolly Adelgids can cause tree death.
Sand Dune Mining
Michigan has the largest assemblage of freshwater sand dunes in the world. Though the majority of Michigan’s sand dunes are now protected through legislation, more than 60 million tons of sand have been extracted from the lakeshore since 1978.
Sand dune mining has been going on for over 100 years. Currently, the Michigan Department of Environment, Great Lakes, and Energy (EGLE) requires a permit to mine any sand within two miles of the shore. Dunes that are deemed “critical” cannot be mined unless the operation started prior to 1987; after that year, regulations have prevented the creation of new mines on critical dunes.
So, what constitutes a “critical” dune? Critical dunes are areas that represent the highest dunes extending along much of Lake Michigan's shoreline and the shore of Lake Superior.
There are about 250,000 acres of sand dunes in Michigan, of which 70,000 are classified as “critical.” The legislature considers these areas of the state to be a unique and fragile resource that provide significant recreational, educational, agricultural, and ecological benefits to the people of Michigan.
Michigan's dune sand is attractive to industries because the sand is clean, having been washed many times by glaciers millions of years ago, so it requires very little processing (cleaning) to remove impurities. Dune sand is also desirable because not much effort is required to mine it since nature has already collected it into large piles. Mined sand is used in foundries to make molds for the automobile industry. It is also needed to make glass and is used for sandpits on golf courses.
The Importance of Conservation
Shoreline dunes are not only one of Michigan’s most spectacular natural features, they are also one of its most fragile. Development and recreational pressures are increasing as more and more people seek the unparalleled scenery the dunes provide. This makes it imperative that people understand and appreciate the environmental sensitivity of sand dunes.
A visit to a sand dune provides an opportunity to experience a unique landscape of natural sounds, smells, and sights. We have a responsibility to protect and preserve this natural legacy for the enjoyment and careful use by our present and future generations.
Sand Dune Legislation
Coastal dunes are in danger of being destroyed by overuse, misuse, and unwise development. They are popular sites for home building, off-road vehicles, and other intensive recreational uses, as well as sand mining and other commercial activities. Such activities, when allowed to continue in uncontrolled and improper ways, will result in dune destruction.
Concern over the wholesale destruction of these unique natural resources led to the passage of Michigan’s Sand Dune Protection and Management Act in 1976 to regulate the sand mining industry. In 1989, the act was amended by Governor James Blanchard to expand regulations to development activities. It established protective standards on dunes considered to be most sensitive. These areas are now legally defined as “critical dunes.”
On July 5th, 1989, Kitchel Lindquist Hartger Dunes Preserve was the site where Governor James Blanchard signed an amendment to the Michigan Sand Dune Protection Act. It established protective standards to “critical dunes.”
The amendment has profoundly influenced the way in which homes are constructed in the dunes – controlling the design and the construction processes, the manner in which they are accessed, and their impact to the surrounding area.
Since its enactment, this law has played a significant role in preserving natural dune areas and stopping abuse. Unfortunately, after giving into pressure from developers and private landowners, Governor Rick Snyder signed legislation in 2012 that loosened up some of the established restrictions making it easier for property owners to build on critical dunes. At this time, it is too soon to tell how much of a negative impact this action will have on this precious natural resource.