The State of Sioux Falls Urban Forest: 2019

With the confirmation of Emerald Ash Borer in Sioux Falls in 2018 it brought with it a lot of questions and concerns with the future of Sioux Falls Urban Forest. To get the full picture of what I’m going to espouse in this article, make sure you read the whole article. This article will reveal my perspective to how I feel the trees within the city are currently doing. Plus, its outlook for the future as Emerald Ash Borer (EAB) and other pests and diseases that attack our trees.

The Sioux Falls urban forest can only dream of having a street lined with trees like this one day. It may happen, but will take several generations to re-grow.

A beautiful tree-lined street. Is it healthy? Does it have good species diversity to be able to withstand something like emerald ash borer?





Current State of the Sioux Falls Urban Forest

More and more information is coming out about the distribution, diversity, and numbers of trees within Sioux Falls. The city is starting to develop and begin to implement a plan to combat EAB. A lot of that information is concerning for the future of Sioux Falls urban forest. When I am driving around the city and looking at peoples trees I see a lot of everything. Some good. Some not so good.

A lot of what makes a great urban forest comes down to its ability to withstand the tests and very severe stresses that come with growing outside of their natural environment (the forest). Now add in the threat of EAB coming in a wiping out an entire family of trees, and it will really show an urban forest’s weakness; Diversity, or lack of it. Therefore, the following list is the pertinent facts that I feel lend to give this current poor to almost failing grade of Sioux Falls urban forest coming into 2019:

  • 40% of city street (parking strip) trees are ash!

    • This is just the street trees within Sioux Falls. I know there is a higher percentage in most peoples landscapes (almost double that amount actually). If not treated all those trees will likely die by 2026 or shortly afterwards based on current projections. Just think, if you have 10 trees along your street, 4 will die within 7 years.
  • Approx. 32% of the street trees are maple!

    • Maple is the most abundant family of trees in the world. That means there is a very high likelihood of a non-native maple specific pest or disease that will come through in the near future and likely do what dutch elm disease did and EAB will do. There isn’t any news or evidence of this yet, but the threat is there. Therefore, having such a high distribution of any one family is bad urban forest management. We have a serious over-planting of maples problem!
  • Approx. 8,000 ash were treated in 2018.

    • There are roughly 87,000 ash trees within the Sioux Falls urban forest (22,000 street, 16,500 park and riparian, and 45,600 private). With about 8,000 treated (about 9%) in 2018, that will not be enough to save the loss in canopy from the other 91%. It is likely that more will get treated in the coming years. In fact, treating every ash out there is unwise, because treated trees must be treated forever to be kept alive. With better planning, public information, and public buy-in prior to EAB coming to town, it is possible most tree owners would not have been cornered in to investing that kind of money into as many treatments.
  • No current or complete inventory of city street or parks trees (one is coming).

    • The lack of a tree inventory prior to this year is the most concerning piece of information and result of the poor grade. We (arborists and just about everyone) have known about EAB for more than 15 years. I remember learning about it in college. Yet when the issue landed in Sioux Falls, the city had no plan at all to deal with the pest. There wasn’t even an inventory to know what to manage.  What was going on for the last 15 years where no plan was put into place? Now I know for a fact this wasn’t the managers faults. It wasn’t the city foresters fault, either. This blatant lack of  planning lies directly with city leaders and burying their head in the sand. Had a plan stared even 5 years ago, we could have saved a lot of money getting ahead of the pest.

Lastly, I can’t place complete blame on the city for this lack of diversity or planning. Everyone who owns a tree has some partial blame. Blame is a strong word, but we need to realize we planted ourselves into this mess. The city didn’t plant all those trees. There isn’t a mass over-planting of maple trees because of professional or city pressure. Too many land and homeowners are ignoring the recommendations and planting too many maple trees. The blame is on everyone. We all need to work together in order to change the current status quo and increase the diversity within the landscape. Maybe even refuse to plant all of one species tree in a landscape. Otherwise, we’re doomed for the same fate; For the third time.


Remember the Ice Storm; The need for federal funding, the concerns over the loss and damage to the trees, and how much it cost the city and its residents to clean up? Remember the damage it caused to the Sioux Falls urban forest? Emerald ash borer is going to make the ice storm look like paper cut when compared to open heart surgery. With the number of ash trees the Sioux Falls urban forest has (had) the financial costs to remove and replace them would have been there regardless of when the process started. But, in stead of slowly losing the ash over the course of what we now know could have been 20-30 years (had a plan been started 10 years ago), we are going to lose that canopy in about 10-15 years.

Then there is the indirect costs. The loss of shade on homes and streets increasing summer temperatures. The loss of wind protection. The decrease in property values. The increased taxes for additional management and recourses to remove and replant trees. The financial burden and strain on home and property owners to treat or remove trees. And the list can go on and on.

Lastly, and very importantly, there is the issue of the dead ash once EAB starts killing trees in widespread fashion in about 6-8 years. Those dead ash don’t stand there like the elms did from dutch elm disease. Ash killed from EAB get very brittle and hazardous. Ash trees dead for more than one year usually just fall over. This issue has created massive safety and logistic issues for arborists dealing with dying trees. Plus, if a homeowner cannot afford to remove a dying or dead ash tree in time, it could lead to major public safety issues. Compounding on the costs of having to deal with this issue.


Sioux Falls Urban Forest  =  D-  (Very Poor)



Outlook for the Future of Sioux Falls Urban Forest

It is not all doom and gloom. I want to make that clear. Fortunately, the outlook for the future is brighter. It doesn’t mean we wont be in for some big challenges, but it sure looks like this is going to be a great opportunity for us to make Sioux Falls Urban forest great. Here is a short list of the things in the pipeline the state and city is doing to make our urban forest a shining example for others to follow:

  • South Dakota State Department of Agriculture has implemented quarantines of ash trees and wood by counties with emerald ash borer.

    • This will slow the spread of EAB around the state and region. It is not a full proof method because people break the law or are ignorant to the restrictions, but it has been proven to slow the spread of EAB in many other states. Click here to learn more.
  • Department of Agriculture will test treated trees from certified pesticide applicators to verify treatments are being done according to industry standards and the chemical label.

    • This will help reduce the chances of unqualified or unethical people from taking advantage of homeowners wanting trees treated. You still need to be careful who you trust, but this step is certainly a good one to verify treatments will work as they should.
  • Sioux Falls is restricting the removal and pruning of ash between Memorial Day and Labor Day.

    • This will greatly reduce the spread of EAB throughout Sioux Falls and to surrounding communities. EAB flies and is most active within that time period. Preventing the movement of the wood will prevent it from moving by vehicle and restricted to the beetle flying. The beetle is a relatively poor flier. Spread will be slow until the populations spikes with this plan. There is even an Ordinance now in place for this specific restriction. A very good plan.
  • Sioux Falls requires an arborists license to operate within the city and raised its license costs to $100 annually ($150 for new licenses).

    • The fee prior to this year was $35. This will help any flyby night or unqualified or non-serious contractors from popping up to take advantage of treating or removing trees within Sioux Falls. I personally would love to see the fee higher with greater requirements to obtain and maintain licensed status.
  • Emerald ash borer populations are projected to peak between 2022-2026.

    • This will give us time to remove a lot of low value and low condition ash trees, slowing the spread of emerald ash borer. It will also give us time to treat the valuable ash. Early treated ash trees are far more likely to survive the major wave of EAB when it hits rather than waiting until signs of infestation are visible. Do not take this as a indication that you can put off treating a valuable ash. If you live within 15 miles of the airport (roughly where EAB is known to be), now is the time to treat valuable ash trees.
  • Sioux Falls will have a completed tree inventory by the end of 2019.

    • This will help immensely with the planning, management, and tracking of the urban forest as the years go on and the number and species of trees change.
  • The city is investing into the Forestry department with equipment and personnel to increase productivity and better manage emerald ash borer.

    • The city has hired a new Urban Forestry Coordinator position (basically a second city forester). Additionally, they have also purchased a wonderful new boom grapple saw that will make tree removals safer and more productive for city workers as well as some other newer pieces of equipment to help keep up with the huge task of ash tree removals.
  • Ash lost in parks and other city areas will be replaced.

    • The city has an aggressive plan to replace ash trees.
  • Sioux Falls is paying for removal and stump grinding of street ash trees.

    • Homeowners will not have to pay to remove ash in parking strip (boulevard) or stump grinding. The site will be ready for replanting plus free up money for dealing with their private trees.
  • The approved street tree species list has changed. Maple and ash are no longer on the list.

    • The list isn’t perfect, but I feel removing maple from the list was a huge accomplishment. In my opinion, we can add even more trees.

 Future Grade = B+


What can a homeowner do to help improve the Urban Forest?

The best thing you can do now is to decide what you will do with the trees you have. Here are some tips to help:

  • Keep the large healthy trees you already have.

  • Remove low value trees or damaged trees.

  • New or replacement trees should be different from what you already have.

    • Try and have no more than 5% be of one species, 10-15% of any Genera, and no more than 20% in any Family of trees.

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