Planting for Resiliency in the Face of Climate Change
As dramatic weather patterns, amplified by anthropogenic climate change, happen more frequently and with greater intensity, we must ask ourselves: can we do more to prepare our natural areas for coming climate changes? The horticulturally inclined might ask themselves how they can build some amount of climate resiliency in their gardens. Often this takes the form of asking if we should be planting species from further south here to “get ahead.”
If only things were so simple! Studies looking at how climate patterns may shift and how plant communities may respond are only beginning to create a body of data to inform our actions. A recent study (Korell et al. 2019) found that of 76 peer-reviewed studies that investigated, broadly speaking, climate and plant diversity only 19 modeled both temperature and precipitation changes. Researchers in this study found that the majority of experiments surveyed modeled more dramatic precipitation changes than what current climate models predict. I highlight this not to minimize the value of the science already done! But simply to illustrate that as simple plant growers (and planters) the data to support pre-emptively shuffling plants around may simply not yet exist outside of very specific contexts.
If we look at some of the research establishing theories for how plant communities may reorganize themselves (Alexander et al. 2016) we see a few models that suggest that any given plant species may find itself interacting and competing with different species than before as plant communities reorganize themselves to account for changes in temperature and precipitation. Or perhaps plant communities may shift to exploit new climactic conditions. That is to say, we may find existing species and communities reorganizing themselves and changing rapidly in ways that may be difficult to predict, even without the addition of new species.
We should remind ourselves too that some of the effects of climate change may not strongly resemble nearby areas. The heat dome over the Pacific Northwest didn’t much resemble Northern California’s mild Mediterranean climate. There is no guarantee that the Northern Virginia of the future will look like North Carolina today. Just today, the Washington Post featured an article about weakening of the Atlantic Meridional Overturning Circulation which could have dramatic global and regional consequences.
Moving plants around comes with risks. Some are obvious, like the spread of exotic pests like Spotted Lanternfly on nursery stock. Other risks are less obvious. Research into common insect herbivores (Tallamy et al. 2009) suggests that even common generalist insect herbivores may specialize in a particular species in any given part of their range. This is likely from long-established coevolutionary lineages within these populations. So, for example, a black cherry from a few states away may not be as appealing to a Luna moth here. The risk is that by introducing plants from other regions -- even of species already present here -- we may not be supporting ecological relationships in the ways we anticipate.
So how then should we build resiliency into our landscapes? The best solution we may not be novel and exciting. It may just mean doing more of what we already know works: good stewardship of our lands. We must protect existing natural areas from stressors that degrade diversity and threaten them — human disturbance and invasive species being the biggest threats. We must protect valuable threatened habitat where possible. We must improve ecologically impaired sites through thoughtful and careful restoration where appropriate. On public and private lands we must remove biophobic deadzones like empty parking lots that create heat islands, vast expanses of lawn that require pesticides and fertilizers and gas-powered equipment to maintain, and entirely exotic landscaping and replace them with diverse biophilic gardens and landscaping features with native plants. We must help create habitat corridors for flora and fauna alike through projects like Homegrown National Park and Watch the Green Grow. And we must protect the genetic resources of our local native plants. By propagating local ecotype native plants, and making them available for use in our region, we maintain the genetic diversity within species to ensure we have a reservoir from which adaptation to climate change – whatever that may look like locally – can happen.