Sunday, January 26, 2014

Toward Harmony with Nature Conference presented by Wild Ones Fox Valley Area

Assisted Migration:  Can Landscaping with Native Plants Help hem Find New Sustainable Locations?
Jim Reinartz

Climate change is expected to alter future environmental conditions rapidly; parts of the current range of many native plant species will not remain suitable to sustain their populations. Plants have colonized new ranges in the past (e.g. following glaciation and in response to a hotter, drier period 7,000 years ago), but during those migrations, the rate of natural climate change was much slower than what we anticipate in the coming decades and the landscape was not as fragmented into small, isolated populations of native species, hindering the natural gene flow that maintains genetic diversity.

Jim asks us to consider whether thoughtful landscaping with native plants might help in some way to reduce the loss of genetic diversity associated with habitat fragmentation, and to help plants migrate to suitable habitat in a changing climate.

Wisconsin’s past climate changes and projected future changes:
  • Warmer winter and nighttime temperatures
  • Frequent hot summer days, heat waves and dry period
  • Earlier last spring frost date and later first fall frost dates extending the growing season 

Change in Annual Average Temperature (F)

  • Increased frequency and intensity of precipitation
  • More rainfall during winter and spring
  • Less snow - lack of consistent snow cover may make conditions more difficult for survival of some plants through the winter

(Note: Short term variability (weather) and extreme events cannot be projected)

Climate models forecast that Wisconsin’s temperature will increase in all four seasons, with the greatest increase in winter. The models project precipitation increases in fall, winter and spring. The combination of warmer temperatures and changing precipitation patterns suggests that we will see a significant increase in the amount of winter precipitation falling as rain rather than snow and that freezing rain is more likely to occur. The magnitude and frequency of precipitation are also projected to increase in spring and fall.

Jim was particularly concerned with the impact of climate change on Wisconsin's "tension zone", the geographic area that marks a change from Southern Broadleaf Forest to Northern Mixed Forest , with species from both areas intermingling in the zone.

Wisconsin Tension Zone

A pronounced tension zone in Wisconsin stretches in a loose S-shape from Burnett County in the north all across the state, ending in Racine County in the south. Wisconsin’s tension zone marks the crossover between the Northern Mixed Forest related to the forests of northeastern Minnesota, northern Michigan, southern Ontario, and New England and the Southern Broadleaf Forest like forests you’d see in Ohio and Indiana. The tension zone is marked by a climatic gradient, with cooler, moister conditions to the north and relatively warmer, drier conditions to the south. Up to the 1800s, these southern conditions were more favorable to higher populations of Native Americans—and they were a greater cause of fire, both purposeful and accidental. This maintained more open conditions in the south.
You’ll know you’re in the tension zone when you’re heading north and … oaks that are dominant in southern Wisconsin, such as Bur, black and white, meet up abruptly with red and white pine as well as paper birch and tamarack swamps that are more characteristic of the north. Shagbark drops out completely and bitternut hickory becomes much less common. You’ll start seeing some birds that are absent or relatively uncommon in the south: common loon, ruffed grouse, osprey, common raven, white-throated sparrow and purple finch. You’ll also encounter northern mammals: snowshoe hare, porcupine, red squirrel, black bear and timber wolf.

Adaptation actions being discussed to address the predicted impacts of continuing climate change include:

  • resistance adaptation actions are defensive actions intended to resist the influence of climate change, forestalling impacts and protecting highly valued resources
  • resilience actions improve the ability of ecosystems to return to desired conditions after disturbances
  • response or facilitation actions help facilitate the transition of ecosystems from the current to new conditions

Jim's presentation focused on a controversial proposal being debated in the conservation community, assisted migration involving moving plants and animals geographically ahead of the projected wave of climate change. Rather than being a resistance or resilience action, assisted migration would be considered a facilitation action and therefore perhaps be considered for the long term. Because we lack basic biological information about many species, including those that are rare, assisted migration may create more problems than they solve.

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