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Can Trees and Sidewalks get along?

 

Tree roots are a common cause of sidewalk damage. Fixing sidewalks are a common cause of tree damage. Fundamentally, trees and sidewalks have competing needs. Sidewalks require an even, compact, bed of soil; otherwise they shift or settle. On the other hand, trees prefer loose, moist, fertile soil into which they can grow. These are divergent needs.

TreesConflict between trees and sidewalks are not new. The issue has been further complicated by planting incorrect tree species or by planting large trees in tree-lawns that are far too small. Current planting practices have corrected many of these issues, but Grand Rapids still contains a population of aging trees. Over time, these trees will eventually be replaced with more city-friendly alternatives. Until then, we have a conflict to manage.

This issue (as well many tree-health issues) is directly related to soil volume. Trees need room to grow. When a tree is confined to a small space it will seek soil, water, and nutrients in the surrounding environment. Areas beneath sidewalks are often moist and become an attractive space for root-growth. Uneven sidewalks are a tripping hazard. Fixing sidewalks is not an option; it’s a safety issue.

Traditionally, the offending concrete slab is removed, tree roots cut, and concrete replaced. However, this approach has become increasingly concerning. Experienced arborists can sometimes pinpoint the decline of a large, mature shade-tree to recently replaced sidewalk squares, road repairs, or similar invasive excavation. Certain species are more tolerant to root pruning than others, but our large, mature trees are less likely to recover from significant damage. Unfortunately, these are often the trees that we wish most to keep.

As a result, many arborists recommend substantial measures to protect valuable trees during construction (e.g. limiting equipment from working beneath the tree canopy). In fact understanding the profound implications to tree health, some arborists have simply refused to cut roots in fear of causing tree death or failure. In cases where the tree cannot be adequately protected, or major roots must be cut, it may be safer and more cost effective to remove the tree in question.

However, there’s been incredible advancements in methods to protect trees and fix sidewalks. In some cases, the lifted sidewalk can be ground to a more even level. In others, mud or a similar material can be placed underneath sidewalk squares to regain evenness. Porous or rubberized pavement is an alternative that allows the sidewalk to “flex” as the tree grows. Some arborists have had success placing various materials underneath the sidewalk during installation that prevents root growth. In either case, there are new and exciting methods available to arborists that promise less tree damage in the wake of sidewalk repairs.

That said, the real fix lies in soil volume. Trees need room to grow. If we wish to have a vibrant, growing tree canopy, then we need to ensure that trees are given adequate soil volume. For a small tree this means: 150 ft2 of soil area, for a medium tree: 250 ft2; and large: 333 ft2. New methods such as structural soils, supported pavement, and appropriate tree species selection go a long way towards ensuring that the right tree is growing in the right conditions.

In Grand Rapids, sidewalk replacement is complicated in that the cost is the burden of the landowner. Understandably, the City is cautious in recommending new practices that may not meet the expected replacement life and shift burdens to landowners. That said, this fails to adequately take into account the value and benefits provided by the tree itself; tree life-span may be sacrificed for sidewalk life-span. For the time being, it may be up to concerned residents to request tree-saving practices and be willing to take financial responsibility if new tree-saving methods do not meet the expected sidewalk replacement life.

Ultimately, many of these practices are more costly. However, we recognize the numerous benefits- from energy savings to community health- that trees provide our neighborhoods. If we wish to continue to experience the fullest potential of these benefits, we may have to accept some additional costs to appropriately maintain the trees in our community.

So, what can you do?

  • If you’re planning construction, consult an arborist to give recommendations to avoid damage to your trees.
  • If a tree has damaged your sidewalk, inquire what additional options are available to prevent cutting or damaging the tree’s roots. Porous pavement, sidewalk grinding, and sidewalk-cutouts may be an option.
  • If all else fails, consult an arborist during the process to develop care and protection recommendations to maintain your tree’s health.
  • You can find a Certified Arborist at www.isa-arbor.com.

 

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