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Designing to Survive – Helping Our Native Plants Adapt to Climate Change

By Laura Hansplant, ASLA, LEED AP, Director of Design at Roofmeadow

Whether I am focusing on green roofs or ground landscapes, I cannot escape the undeniable: Climate change is making an impact. What can designers and landowners do about it?

I’m going to start with an essential distinction.

Scale matters.  The choices we make about landscapes at a regional scale matter a lot.  Our ability to conserve large natural areas – such as habitat preserves and greenway corridors – is important. These big habitats offer opportunities for native species that we just can’t replicate, ecologically, within our developed landscapes. Integrating these large-scale habitats demands a coordinated, committed effort among civic leaders, conservancy organizations, and advocacy groups – an arduous campaign well worth the effort. (Read more about how regional land conservation can be a corner stone of climate change mitigation: Ontario’s Greenbelt strategy and Carolinian Canada.)

1-scale matters

My scale, however, has a much smaller footprint – a reality that applies to most people I know. Can we impact climate change when designing a single green roof, managing a meadow, or building a cutting garden at home? As you might guess, I have a few thoughtful recommendations.

1.  Incorporate native plant communities into the places we live and work.  Just any collection of native plants will not do. Deliberately select a suite of native species that play together well in the same, umm, mulch bed.  Specifically, look to reference plant communities in your ecoregion, and in ecoregions south, for reference communities likely to adapt well to the specific geology and soils of your site.  Also consider how plants knit together in an integral, layered way, leaving less space for weeds (and less time spent managing them). Happily, pollinating insects and birds fare better when we design with a broad range of plant species. .

5-East Falls-infill

2.  Preserve genetic diversity.  Many plants sold in nurseries are reproduced vegetatively, which means they are genetically identical. Genetic diversity imparts resilience to extreme weather and opportunistic pests. So, to foster resilient landscapes, specify seed-propagated, straight species instead of cultivars.  Look for regional ecotypes which offer specific adaptive traits.

2-genetic diversity

3.  Leverage the geography of plant production. People are probably the biggest movers of plants around the regional and national landscape.  Often, plants have been shipped around the region, if not across the country, by the time they arrive at a project site.  In light of these logistics, leverage your plant ordering for good. Climate change dynamics are suggesting that native plant communities might not be able to migrate fast enough to keep up, but the design community can lend a hand. For more common natives, order appropriate plants from southern ecoregions and help in a small way to shift regional populations northward. (I propose this concept of a human assist to plant migration with full deference to the implications of this strategy for rare plant conservation.)

Can you distinguish the cultivar from the straight species?

Can you distinguish the cultivar from the straight species?

4.  Allow plant reproduction in designs.  We don’t often allow plants to reproduce in the landscapes around our buildings.  I think it’s time to loosen up a bit. What is the point of promoting genetic diversity, recognizing regional plant provenance, and leveraging regional production patterns if we don’t allow plants to reproduce?  Landscapes are not static; our expectations must shift to align with the way nature works and evolves.  What if we took a more adaptive approach, one that made use of (managed) change as a healthy part of our site maintenance practices?

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5.  Foster healthy soils.  Take a ‘roots up’ approach to site stewardship that promotes healthy living soils as the foundation of a low maintenance, healthy plant community.  I’m intrigued by the potential of soil transplanting (in large intact blocks, not mass grading) as a salvage and restoration technique that carries, living and intact, herbaceous plants and seedlings, seed bank, soil microorganisms, and soil structure.

6.  Green our urban environments with a new generation of green roofs and high performance stormwater Best Management Practices.  Recent advances in green infrastructure design offer a stable, healthy approach to managing rainfall while simultaneously providing a wide range of other environmental services (including carbon sequestration). Check out Philadelphia’s innovative green infrastructure program and recent design competition. Green roofs can be lightweight, relatively inexpensive, and easily implemented over large areas – think urban heat island mitigation! Alternatively, deep soil green roofs can be designed for habitat value – think meadow roofs and wetland roofs!   Both types add value to our urban environments.

Green roof on The Radian, Philadelphia, PA

Green roof on The Radian, Philadelphia, PA

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