Learning a Climate Change Lesson

Issue: 
January-February 2008

WHEN THE ICE STORM OF 1998 struck eastern Ontario, people were traumatized. Michael Rosen, President of Tree Canada, said, “I survived.” Michael was without hydro for eleven days. People and livestock died. Houses and barns were damaged. When the hydro lines were repaired and the emergency past, trees were the lasting reminder every fall of the trauma. Ice storms are a normal part of Canadian weather. If climate change predictions come true, we will see more ice storms and more extreme weather. But Michael believes it will be better next time.

The world has experienced climate change in the past. There are extensive records proving much of Ontario was at one time under ice, once under water, there were mountains where today we have Bancroft, and it was at another time a lot warmer. Those changes took ages – this time it is happening fast. This time it is unique. With this climate change we have to alter our patterns of behaviour and the ice storm of 1998 was an opportunity amongst the devastation to discover just what we can do to make a difference. And handle it better next time around.

Be Patient
It takes only a few minutes to cut down a tree but a lifetime to replace it. Once it was believed that a tree with 50% crown damage should be removed. Rosen says, “Believe in the resilience of trees. Our trees and ice storms evolved together. Don’t rush to cut trees down.” Michael is speaking from experience. He has a 50 or so year-old birch on his own property that sustained 75% damage, “And it is still alive. I thought it might live a couple years after the storm but it leafs out every spring.”

Sylvia Greifenhagen, a research forester with the Ontario Forest Research Institute (OFRI), participated in a literature review after the ice storm. “Young maples with 85% crown damage were invaded with decay fungi in a 1940s study. The timing of an ice storm affected its outcome. It was very cold after the storm so the wounds dried before spring.”

In general, however, it is recommended the cut off mortality rate is 75%.

Crown damage can be estimated aerially or visually for forest stands but more accurate calculations are determined for landscape or individual trees by actually counting branches. Removal of dead trees may lessen the probability of beetle infestation.

Jim McCready worked with MNR in Kemptville after the ice storm. He noted many of the trees were over trimmed or trimmed improperly. Sometimes “the stub was left” or the branch collar was removed leaving them vulnerable to disease. Jim said he wasn’t able to get to many trees until June and at Carleton Place it was three years before trimming was complete and “that was a good thing.” Trimming late allowed the arborists to see exactly what branches were killed.

Greifenhagen said, “Trees have evolved to survive numerous attacks by fungi and insects and have internal defense mechanisms that help them fend off these organisms. The susceptibility of a tree to insects or disease depends on the severity of the damage caused by the ice storm, the species of tree, the previous health of the tree, and the species of fungi and insects involved. Trees do have an amazing capacity to heal wounds and “wall off” decay. A “wait-and-see” approach for the first few years after trees are damaged will give you a better idea of how they are reacting to the damage. Decay moves very slowly, therefore immediate action is not required unless the damage has caused safety hazards.”

Storm Opportunists Necessitate Proper Planning
Michael Rosen explained what happened in eastern Ontario. Motels were full of people from out of province and out of country going door to door saying things like, “the tree will fall and kill your kids,” or “the branch will fall through your house and cut off your hydro – again.” It is hard to combat that level of fear mongering.
McCready believes the solution is like being a good scout and “be prepared.” Planning for tree emergencies after extreme weather events starts at the municipal level long before the storm starts to blow. Jim suggests meeting with municipal leaders ensuring the municipality understands why arborists should be certified and why they need a list of certified arborists in their emergency plan that can be provided to the public upon request.

Second when an emergency occurs, use mass email (have a contact list prepared ahead) and meet with special interest groups as soon as possible. Include all local certified arborists, federal, provincial and municipal leaders, forestry workers, researchers, Tree Canada, and local affected organizations like maple syrup producers, apple or Christmas tree growers. Establish a plan for the present situation and detail your priorities and goals.

Finally, communicate with the public as a united group. Michael Rosen said the public level of sophistication around tree maintenance is limited. They are suspicious of those with a conflict of interest and are more willing to trust a ministry opinion instead of someone who derives an economic benefit from pruning trees.

There is research from the US that indicates rural dwellers hold different opinions then urban residents (no big surprise). This can’t be compared directly to Canadians but it does imply that one solution will not fit every region and information may need to be sorted differently after the next ice storm depending on its location and the groups of people involved.

When you are speaking with the municipal office you might remind them that well managed trees – those pruned appropriately on both private and public lands were noted to cause less disruption to homes, hydro and roadways then those left untended. I didn’t find any studies on the cost benefits of prevention, but the costs of the damage to infrastructure were high. One forester noted that Norway maples suffered more damage then the indigenous sugar maple. He stated that trees adapted for our climate were able to shed the moisture better. He couldn’t prove it but at the time it seemed obvious that trees that shed water naturally were better off then those with multiple places for moisture to collect and freeze. Basswood, butternut, poplar, silver maple and black cherry sustained the highest levels of damage. Trees with forked branches in clumps were the hardest hit. It’s an obvious preventive solution to think about species type before planting near any structure or hydro lines.

Sugar Maple Research
A significant amount of Ontario’s ice storm research is on forests, not landscape trees. However, much of the information gathered has wide applications.

The ice storm was an opportunity for Tom Noland, a researcher with OFRI, and other scientists to study trees under stress from an extreme climate event as climate change begins. In Ontario, 604,000 ha of hardwood forest, largely sugar maple, were affected by the 1998 storm. Crowns suffered from 7-72% damage. This dramatic example of nature’s power allowed measurements of the damage, recovery rate and how interventions worked.

Tom applied fertilizer treatment studies on maples after the storm. His goal was to determine the affect of fertilization on syrup production not growth, so he used dolomitic lime (calcium, magnesium), phosphorous and potassium without nitrogen because it can affect the taste of the syrup. Follow up measurements proved sap amount per tap and sweetness were reduced by the damage but it wasn’t at consistent levels during the test years. The fertilizer did temporarily boost the growth rate, but it did not affect the root starch sugar levels, sap production, sap sweetness or tap hole closure rates. In the follow up study, crown damage greater then 25% to maples reduced syrup production by 20-30% for up to six or seven years, though not consistently every year. In addition, fertilization did not improve the ability of the maples to recover from the effects of the ice damage and regain their full syrup production capacity.

After the ice storm, reduced tree canopy allowed increased sunlight to reach the ground. As a result, there was an increase in near ground vegetation. “Species richness was initially reduced by vegetation management. Species richness levels on treated plots were comparable to or higher than those on untreated plots by two years following treatment.” Ice Storm Damage, by Lautenschlager and Winters, says “the combination of competition control and fertilization increased growth of ice-damaged maple the most.”

Tom Noland translated, “Controlling competing vegetation around the damaged trees may be the best thing that owners can do. This significantly limits competition for water, nutrients, and to a certain degree, light, allowing faster recovery.”

William Parker (Bill), also with OFRI, studied crown damage effects on environmental conditions of the understory after the ice storm. His research was on sugar maple forests managed for syrup production and he did not directly study the relationship between the understory and crown recovery so it can not be related directly to landscape trees, but it does make for interesting review. He noted the damage to the overstory in forests allowed higher light, elevated air temperatures and lower humidity in the understory. Fertilization and competition control had comparatively small effects on the understory microclimate.

Parker said, “Replacement of crown tissues takes several years depending on the level of damage. Recovery and regrowth of new branches and leaves … depends on the health and energy reserves of the tree and the growth resources available … and whether the trees are stressed by something else prior to or after the ice damage. Soil moisture levels tended to be lower where more crown damage occurred. This suggests that in more heavily damaged stands, the trees were using more water.” But, the affect of soil moisture changes on recovery were not addressed in the study.

Cathy Nielsen was one of the researchers who looked at the effect of past management on hardwood stands. Again, it is forests not managed landscapes being considered. Research in Maine showed that heavy thinning on plantation trees including yellow birch and white ash increased the damage by 15%. Cathy’s study on hardwood stands in eastern Ontario with light to moderate damage revealed no difference whether the lot was managed or unmanaged.

A final problem was noted. During clean up, the heavy equipment used rutted the soil, caused root shear and disruption of the root zone. There were also additional abrasions caused to the stems. Again, waiting at least until late spring for non-emergency cleanup might have reduced the trauma.

The Opportunity
One of the biggest lessons Michael Rosen said he learned from the ice storm was to: “Brush up on safety! Ice storm damage is the worst type of work. Concentrate! Keep in shape. Keep current with educational courses and practical demos. It is slippery and there is tremendous weight involved.” Being prepared works – and it just might increase your business.

Additional Information

Public Resources: Explaining the Intracacies
During the ice storm of 1998, Shell financially supported the publishing of pamphlets on tree care for public distribution. Copies can be viewed at www.treecanada.ca/publications/pdf/operation_releaf.pdf.

Another good handout is Caring for Ice Damaged Trees (LandOwner Resource Centre): www.lrconline.com/Extension_Notes_English/pdf/icedmgd.pdf. In addition to providing good information, publications like these underscore the need for proper tree care – something which the average homeowner doesn’t have time to do himself!

What to Plant? Species Decisions
Some climate change forecasts say that sugar maples will decrease by 98.5% across the northeastern US and southern Ontario moving instead up to 700 km north. This is due to the expected increase in temperature, evaporation and increased frequency of extreme weather events. Tree Canada said they have not changed their planting policy and continue to plant trees only in their zone as the saplings have to survive today’s weather. However, they are considering moving seed to the extreme north of each zone. The debate on whether to plant for today or tomorrow continues as tree decline pro-gresses in Ontario.

Predictions: What the Future Holds
Weather predictions are sometimes wrong. They are predictions, educated guesses, and forecasts. What we know in southern Ontario is that the climate has changed. We know the status quo is no longer acceptable. Having stated the obvious, there are at least 30 credible predictions for climate change. Ontario’s Climate Change Research Report CCRR-05 discusses two. The two overlap to some degree so for simplicity I am quoting A2. For copies of the maps of Ontario’s weather predictions, contact the Ontario Ministry of Natural Resources.

Most of southern Ontario will have summers that are two to three degrees Celsius warmer by mid-century. By 2071, from the Bruce Peninsula to the Ottawa Valley will experience the types of hot summers that presently occur only in Windsor and Essex County. South of a line from Owen Sound to Pembroke will receive 10% less rainfall. Rainfall will increase by up to 10% north of that line. Between 2011 and 2040, winter temperatures in most of southern Ontario will warm by one to two degrees Celsius (Ottawa is the exception.) After 2011-2040, southern Ontario will receive up to 10% less cold season precipitation. Central Ontario can expect 10-20% less cold season precipitation.

From Forest Information Paper No. 154, increased frequency of extreme weather events. Drought, rain, hail and ice, and windstorms are predicted to increase in frequency. For example, an event that now has a probability of occurring every 30 years may begin to occur every four or five years. Increased carbon dioxide levels may stimulate growth of some fungi that cause plant diseases. Plants stressed by drier soils and more extreme weather will have increased disease susceptibility.

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