Along the east side of a block of North 90th Street stands one particularly large and stately ash tree.
Around it is wrapped a hand-lettered sign that says, "Please do not cut down our TREEs." The "s" is tiny, implying that the supplicant prizes all the trees on the street, but this one more than all others – probably because it stands in front of his or her home, but also because it such a fine specimen.
Surely city foresters would be moved by that argument – and well they might. The larger, more sturdy and more shapely a tree is, the more it is worth to the community.
That is not just in aesthetics, but in pure economic terms.
But the fact is, that robust ash could be chosen as the first to come down. The reasons are complex; the explanations might be difficult to accept.
Trees are going to be lost; how many is uncertain
As moves forward, a number of street trees are going to be lost. The initial estimate was 240, but through a careful analysis of the project, the minimum number was reduced to 60.
That is a best-case scenario. The actual number of trees destroyed could be somewhere between those figures.
The dynamics begin something like this, according to City Engineer Bill Wehrley:
- For a contractor, the easiest choice is often to clear-cut an entire street rather than to deal with working around the trees;
- However, contractors have to pay a penalty to the city for each tree they destroy – perhaps as much as $30,000 for a large one;
- So, contractors have learned to pre-assess the situation and write their estimated penalties into their contract bid;
- Therefore, city engineers and foresters have learned to do extra analyses of their own and set project design specifications intended to minimize the damage.
But, in the end, all bets are off when the machinery actually starts to roll, the trench is dug, it starts to rain and the walls threaten to collapse, Wehrely said.
Or when digging past a tree, so much structural root growth is encountered and destroyed that the tree is in danger of falling onto a home or into the street.
Or in the event of any number of other unforeseen scenarios that could crop up.
Wehrley said that first estimates showed the city could have lost $1.5 million worth of trees in the Meinecke Project, with attendant haggling between city and contractors over who would be responsible.
Parks and Forestry Superintendent Ken Walbrant was asked to work with engineers on an assessment of the value of individual trees and blocks of trees along the route of construction.
If, for instance, in stretches where it appeared that trees on both sides of a street would be lost, the excavation could be jiggered slightly to one side to save the other, where would be the greatest gain, or the least pain?
Ash trees draw the short straw
Walbrant applied his own set of criteria, and among those was the looming arrival of a tiny green insect – the emerald ash borer.
It is Walbrant's educated opinion that within five years, despite any efforts to stave it off, the emerald ash borer plague will have reached Wauwatosa, and every one of the thousands of ashes in the city will be at high risk for infection and fatality.
(In fact, when the emerald ash borer was discovered in the region, the city sought bids for a contract to remove all ash trees at once, thinking they could be sold for pallet wood, pulp, chips, biomass fuel or something, and the proceeds applied to replacement trees. There were no takers.)
Therefore, all ash trees score low on the scale of trees worth saving.
As Wehrley put it, speaking for Walbrant's analysis, if it's between this ash and that elm or that maple, the elm or maple is going to win.
If it is between this maple and that corktree, the corktree is going to win, because the city can't get new corktrees anymore.
Your sewer line could be feeding that fine tree
Which is not to say that the big, stately ash mentioned above is doomed now, although Walbrant believes it is doomed eventually to the borer (ashes can be treated for the disease, but the treatment is expensive and not guaranteed effective).
But if that ash is in a segment of the project where a choice has to be made between it and another less risk-prone species across the street, the ash will lose out in spite of its apparent vigor.
Even with that explanation, does it seem right that this one tree that has so outstripped its neighbors in height and girth should be squandered?
Well, you have to ask how it got that way. Was it simply a genetically superior specimen? Or did it, among all the trees on that block, happen to somehow strike upon a rich source of water and nutrients?
Was that source perhaps a sewer lateral that its roots invaded? Very likely so.
Once upon a time in Tree City
Wehrley pointed out that for all on city sewer lines in the Meineke Project, it won't protect any individual home if that home's lateral is blocked by tree roots.
Among trees notorious for reaching their roots into sewer lines and feeding off them are green ash and Norway maple.
Old-timers on the forestry staff still tell of the "deal" the city was offered on green ash trees when the streets of Tree City Wauwatosa were lined with huge American elms for block after block after block, nearly all of them succumbing at once to the Dutch elm disease.
The ash trees were so cheap they couldn't be passed up. Nurserymen said they were fast-growing and would soon replace the lost elms. The city bought them by the thousands, and also Norway maples and European lindens and honey locusts.
There began a counterintuitive regime of trees in Tree City. Consistency and continuity was the goal, as if to recreate that palace guard of elms that had stood so long. (Did anyone stop to think that if rows of one type of tree could all fall to one exotic disease, so could another? Apparently not.)
Forestry mapped out Wauwatosa and assigned one of those four species to every block, ashes prevailing in sheer numbers. For many years, if the tree in front of your house was destroyed, damaged or diseased, you had no choice but to see it replaced with another of the same type. (Put another way, you had a choice of four species, so long as it was the one you already had.)
The trouble was, every one of those species was wanting in some way. The green ash, as it turned out, is an easy tree to start in the nursery. It naturally grows in floodplains and is prolific there. Give it rich soil and plenty of water, constantly, and it thrives.
In the dry and indifferent or downright awful soil of street rights-of-way, most of them grew poorly and produced unsightly specimens when they grew at all.
The Norway maples fared better, but they proved to be voracious feeders, sucking the life out of lawns and siphoning from sewer lines wherever they could find them.
Locusts were erratic, growing well here and poorly there, and everywhere producing the thinnest of shade.
Lindens showed themselves to be subject to cankers, which of course they passed from one to another when planted side by side for blocks on end.
Lessons learned for projects to come
That lesson, of the dangers of monoculture, has been learned by city foresters. The roots of trees intertwine and actually bind, or graft, to their neighbors, especially if they are of the same species. And if they are of the same species, any disease they are subject to will surely pass from one to another as if invited.
Wehrley said that residents whose street trees are taken down in the Meineke Project will have a choice of a number of species to replace them.
The same criteria will likely be applied if, as is likely, there are trees lost when the city eventually moves forward with the East Tosa Project, which is still in preliminary stages of development.
East Tosa, Wehrley says, is "the 800-pound gorilla" of sewer upgrades in Wauwatosa. It has older infrastructure than the Meinecke area and is more dense. East Tosa, comprising the 1st and 5th districts, accounts for about one-quarter of the households in the city.
It will cost somewhere between $32 million and $80 million, with uneasy estimates on the high side.
When the design phase of that project gets under way, it is likely that trees will again become an issue, and the answer will be the same.
City Finance Director John Ruggini was direct and succinct: "I place more value on the homes (that are flooded) than on the trees."
In other words, city property values can survive the time it takes to replace trees better than it can stand home values depressed by constant and unmitigated flooding.
So the streetscapes of some neighborhoods may become a bit motley, a tad untidy to some eyes.
The city may lose something of its old regularity, with long lines of identical trees lining every street, but it may gain in the overall health of its urban forest.