Ruminations on Tree Planting and Prairie Conservation

Trees are great, but trees in and around prairies can negatively impact habitat quality for many grassland plant and animal species and provide points of introduction for invasive species.  Encroachment by trees has become a major threat to prairie conservation in many landscapes.  

A few months ago, I cut across the courthouse lawn on my way home from the office (I was walking – it’s a small town).  On the west side of the courthouse, there are a number of statues and other monuments memorializing veterans of various wars.  In the midst of those, however, is a very different kind of memorial (pictured below).  This plaque-on-concrete memorial got me thinking – yet again – about our relationships with trees, our desire to plant and care for them, and how that affects our former, current, and future relationship with prairie.

We love trees so much, we use them to memorialize important events and people in our lives.  Sometimes, we then create memorials to honor people who plant trees!

We love trees so much, we use them to memorialize important events and people in our lives. Sometimes, we even create memorials to honor the trees and the people who planted them!

I live in Nebraska, home of Arbor Day.  Early European settlers of Nebraska were enthusiastic tree planters for both practical and aesthetic reasons; our legislature even designated us as “The Tree Planters State” back in 1895.  There were good reason for all that tree planting.  It’s certainly nice to have shade around one’s house and yard, and a grove of trees provides a valuable shield from strong winter winds for both homes and livestock.  In addition, early settlers found the open prairie lacked adequate wood for fuel and building materials.  However, despite the numerous practical uses for trees, I think most tree planting was and is done primarily as a way to make the landscape more visually appealing.  People just like trees.

This brings me to my contemplation of tree planting and prairie conservation.  Research has shown that when given a choice, people seem most attracted to the aesthetics of a savanna-like landscape – one with scattered trees and short grass.  That mindset is evident in the way we design our yards and parks.  Not only do we enjoy having trees, we really like to plant them ourselves.  We gain immense satisfaction from the simple act of digging a hole and plopping a seed or small seedling in the ground, knowing that we and future generations will be able to watch that tree grow skyward.  The trees we plant often become almost family members in the way we celebrate their growth and mark time by how big the trees were when such and such happened.

The landscaping around the Hamilton County, Nebraska courthouse (where the above plaque is located) is a great example of the kind of scattered trees/short vegetation landscape humans find aesthetically appealing.

The landscaping around the Hamilton County, Nebraska courthouse (where the above plaque is located) is a great example of the kind of scattered trees/short vegetation landscape humans find aesthetically appealing.

This brings up two issues for those of us working to conserve prairies.  First, we’re starting from a handicapped position when we advocate for prairie conservation because prairies are not what most people visualize when they think of natural beauty.  Given the choice between a treeless grassland and a park-like landscape dotted with trees, most people would choose the wooded park as a site to photograph, hike or picnic, or build a house.  In fact, there are countless examples in which people buy a small patch of prairie for a recreational property and immediately plant numerous trees to make it “look nicer.”  We really haven’t changed much from our European settler predecessors in that regard.

Second, we haven’t yet found a prairie-related analog to tree planting; a simple activity that creates something people can take ownership of, love and nurture.  Planting trees is so easy a child can do it, and with very little investment of time or money, someone can establish a couple trees that become treasured landmarks or memorials – – which further reinforces people’s love of trees and wooded areas.  In contrast, planting prairies is fairly complicated and requires more space.  It also takes a few years for a planting to grow out of its weedy phase and start to look like a prairie.  Prairie planting can certainly be rewarding, but it’s not nearly as simple, accessible, and instantly gratifying as tree planting.

Many people find wide expanses of open prairie impressive, but not alluring.  How do we get people to care about and nurture landscapes and ecosystems they have to work to appreciate?

Many people find wide expanses of open prairie impressive but not alluring. How do we get people to care about and nurture landscapes and ecosystems they have to work to appreciate?

So how can we help people connect with prairies in the same way they connect with trees and wooded landscapes?  I don’t have all the answers, but here are a few ideas.

1) We need to encourage more people to spend time in prairies and make sure they enjoy themselves when they go. It can be a definite challenge to convince someone to take a walk in a prairie.  Even worse, when people do step foot in a prairie, many are unimpressed because they don’t really know what to look for or how to appreciate what they’re seeing.  As a result, they often walk away with an even less favorable opinion than before they came.  “It was just a lot of grass!  And I was pulling ticks off myself all night!”

A good naturalist and interpreter can lead someone on their first prairie excursion and make it a positive and thought-provoking experience.  There is no substitute for the expertise and enthusiasm of a good leader, but there aren’t enough of those people to go around.  Several Nebraska Master Naturalists approached me last year with an idea to create a “Prairie Exploration Guide” – a pamphlet/booklet designed to help newcomers to prairie see the beauty and complexity they might otherwise miss.  The guide is still in the development stage, but I have high hopes that it will be a useful tool when it’s done.

2) Using native prairie plants in landscaping is becoming increasingly popular. The public’s concern over population declines of bees and monarch butterflies is helping to spur the movement, as are issues such as water conservation.  There is no question that getting the public to buy, plant, and appreciate native prairie plants in their backyards is a major step toward building a prairie conservation constituency – and backyard prairie gardens also make real conservation contributions on their own.  Significant obstacles still hinder the movement, especially our cultural norms about what yards and gardens are “supposed” to look like, but I am optimistic about the future.

3) One successful method for engaging people in prairie conservation at our Platte River Prairies has been through seed harvesting. People identify with both the value of seeds and the idea of restoring lost habitats.  Harvesting seed is a tangible way people can contribute toward something important; they can measure that contribution by the amount of seed piling up in their buckets.  Ideally, harvesters come back and help plant the seed they picked, and then visit regularly to watch the prairie planting develop over time.

I hope that helping me harvest and plant seeds at our family prairie will help my kids develop a love for grasslands.

I hope that helping to harvest and plant seeds at our family prairie will help my kids develop a love for grasslands.

Along those lines, one of the most inspired strategies I’ve seen to engage people in prairie restoration was being done by Wayne Pauly in Dane County, Wisconsin.  I went on a tour of some of his prairie restorations back in 2004 and was very impressed with both his plantings and his involvement of volunteers. Most particularly I liked Wayne’s strategy of having volunteers “paint the prairie” with seeds during prairie plantings.  He’d give each volunteer a bucket of seeds of one prairie wildflower species and let them decide how and where to plant those seeds – allowing them to create a pattern or design of their choice (thus the idea of “painting”).  That is a brilliant idea, and one that should not only be fun on planting day, but should also draw those volunteers back in subsequent years to view the results of their work.

Humans have a long and strong relationship with trees, one that is likely embedded within our DNA.  Tree planting is an easy, accessible, and tangible way to contribute something to the natural world.  Unfortunately, tree planting doesn’t do anything to help prairies, and can sometimes be counterproductive if trees are planted in or near open grassland.  If prairie conservation is to succeed, we need to get the public excited about grasslands and combat the perception that prairies would look a lot prettier if they just had some trees growing in them.  More importantly, we need more strategies that actively connect people with prairies and give them the same sense of fulfilment they get from planting trees.  I think we’re getting better, but we have a long way to go.

A Prairie Ecologist’s Perspective on Arbor Day

Today is National Arbor Day – a holiday initiated by J. Sterling Morton right here in my home state of Nebraska.  The idea of Arbor Day is to encourage the planting of trees. However, as a prairie ecologist, I spend considerable effort trying to keep trees from taking over the prairies I manage and/or care about.

As a result, I have some mixed feelings about Arbor Day.

A cottonwood tree in a Platte River prairie at sunrise.

A cottonwood tree in a Platte River prairie at sunrise.  Beautiful, but not without some impacts on prairie ecology.

I don’t harbor any particular enmity toward trees themselves.  In fact, some of my favorite places in Nebraska have fantastic woodlands, including The Nature Conservancy’s Rulo Bluffs Preserve and Niobrara Valley Preserve.  I also really like the trees in my yard – especially the one that produces a big crop of pie cherries each year!

On the other hand, I don’t hesitate to use all necessary force to remove trees from grasslands.  Why?  There are numerous reasons.  Here are a few examples:

– The shade from trees changes the microclimate underneath them, suppressing the growth of many prairie plants and favoring others, including some nasty invasive species that can then spread into prairies.

– Trees completely change the habitat structure of a prairie, making it unsuitable for many wildlife species that rely on wide open habitats.  As trees and shrubs increase in density, prairie animals are forced out.

– Many grassland birds avoid nesting near woodlands, or even lone trees.  There are multiple reasons for this, but a big one is the abundance of predators that hang around in and under trees.  A line of trees along the edge of a prairie creates a wide “dead zone” within which very few prairie bird species will nest.  In landscapes where most prairies are already small and fragmented, the loss of that additional habitat can have serious consequences.

– Once trees and shrubs become established, they tend to promote the establishment of more.  Some spread by rhizomes (underground stems) and all of them are good perch sites for birds, which drop seeds out both ends onto the ground beneath the trees.  Once on the ground, shade from the trees reduces the vigor of prairie plants and helps woody seedlings thrive.  Dense tree and shrub patches can also become fire proof because their shade prevents grass growth beneath them – and it’s grass that carries fire.

Burning prairie can suppress the encroachment of trees, including eastern red cedars.

Burning prairie can suppress the encroachment of trees, including eastern red cedars.

Woody plants, including both trees and shrubs, have always been good at invading prairies but, historically, fires and dry climate helped keep them from becoming established across most of the grasslands of the Great Plains.  Today, fire suppression, landscape fragmentation, and even changing levels of carbon and nitrogen in the atmosphere are giving trees the upper hand.  As a result, my staff and I (ok, mostly my staff nowadays) spend an inordinate amount of time cutting trees down, burning grasslands to kill trees, and treating trees with herbicides.

Can you see why a holiday that promotes tree planting – especially in a grassland state like Nebraska – might make me a little nervous?  There’s absolutely nothing wrong with planting trees, but the kind of trees being planted and the location they’re planted in makes all the difference in the world.

If you live near a prairie, here are two important tips to consider as you prepare to celebrate National Arbor Day by planting a tree (or lots of trees).

1. Do some research on the tree species you plant.  Some species, such as Siberian elm, Russian olive, Autumn olive, and other non-native trees and shrubs can be very invasive in grasslands, quickly spreading by seed far from the parent tree.  A quick internet search using the name of the tree and the word “invasive” will tell you whether or not the tree species you’re considering is one that could cause problems.  However, even many native trees can spread into grasslands, so that leads us to…

2. Carefully consider the location of your proposed tree planting.  As mentioned earlier, even a single tree, let alone a row along the edge or (heaven forbid!) through the middle of a prairie can wreak havoc on grassland birds and other species.  Prairies and their plant and animal inhabitants thrive in wide open habitats; adding trees to those habitats can really mess things up.

By all means, plant trees in your yard, around your farmstead, or in a local park or school.  Trees provide shade, habitat, food, and aesthetic beauty to cities, towns, and acreages, and you should feel good about contributing toward those things.  However, as you celebrate Arbor Day, please don’t forget about prairies, the plants and wildlife that rely on them, and the hard-working prairie ecologists and land managers trying to conserve them.


Happy Arbor Day!

(please celebrate wisely)