RANGE SHIFT - PLANTS ARE ON THE MOVE
Fair warning readers, this article is unapologetically more “sciency” than the usual, and for good reason! There’s a saying that change is the only constant in life, and in this article, we’re going to talk about a particular type of change happening with many species – range shift. We’re going to define it, discuss what this could mean for the plants we all know and love, and what we should be doing about it.
Let me preface this by saying that there are many smart people that dedicate their entire life’s work to research this topic - whether that’s identifying when range shift is happening, predicting it or determining its impacts. So, to try and cover this in a blog article is admittedly a bit sporty, but it’s so important that we’re going to try!
Range Shift Defined
To understand range shift, we first need to understand what is a range. An encyclopedic definition for a species’ range is the geographic area where all members of that species are found. Technically, all living species have a natural range, not just plants, but we’ll just focus on those here. Sometimes certain plant species are introduced and cultivated so much by humans, like say a Lantana strigocamara, that it can become tricky to identify the plant’s natural range, but that’s a topic for another article.
Some species have a very small natural range, while others have a larger one. For example, Florida is home to over 100 endemic plants with smaller ranges, like the Florida bellflower or Curtiss milkweed, that are only found in certain areas of the state. Conversely, we have other species like the loblolly pine that has a wider range and distribution throughout a dozen states in the southeast United States.
Curtiss’ milkweed (Asclepias curtissii) courtesy Emily Bell
Regardless of the range size, it’s important to know that it’s in this goldilocks zone that these plants have the right habitat with a balance of resources and predators, weather, and climate for their survival. Scientists assess species range periodically, and when they notice that some are being observed consistently outside their known native range, they start to suspect that a range shift is taking place. Cue suspenseful music.
Range Shift – What Does It Mean For The Plants?
Range shifts can happen naturally over time if conditions dictate for a certain species in their environment. The range can shift by getting larger, smaller, or moving altogether. So why is range shift such a hot topic now for plants? Well, because it’s happening a lot faster, and we’re all noticing. We know that climate is a major driver in range shift and well, yes, that’s changing faster too. So, what’s a plant to do? Pack up and move! To make matters more interesting, according to a 2022 study by the National Science Foundation (NSF), over 75% of plants globally exhibit “climate fidelity”, which means they prefer to migrate to follow their preferred climate. Others however, prefer to stay put, tough it out, and aim to adapt in place. For those on the move, scientists predict that they are headed towards the Earth’s poles, in search of cooler climate conditions. As gardeners, this means don’t hit print on that trusty USDA hardiness zone map yet, as it may change more often than we’re used to. We may notice in our lifetime nurseries may carry new plants that have usually never thrived in our area.
USDA Hardiness Zone Maps – Comparison of 1990 to 2012 Maps courtesy www.nwf.org
But you must be thinking now, how exactly do plants pack up and move? With a little help from their friends! Birds, for example, can carry seeds to new, more far away locations, as can the wind especially during storms and hurricanes. These seeds now arrive in a more favorable climate condition for germination and establishment. As plants shift their ranges, they also impact other species and ecosystem processes in their new area, and leave a gap in the areas they leave behind. You see how this can have a massive cascading effect in ecosystems? It’s messy, and difficult to predict.
Species undergoing range shifts have impacts to other species and processes - Figure from Pecl et al 2017.
Range Shift – Can I Do Anything?
The truth is, we don’t quite know exactly how this all plays out, but we can take some actions. For starters, anything that helps pump the brakes on the rate of climate change is a good thing. That aside, remember those endemic Florida plants I mentioned with smaller ranges? Those need our help the most as they have unique habitat requirements for survival often not found elsewhere. Migration for them is most difficult and extinction is a very real threat for them. Helping conservation efforts for these natural populations is helpful, for example by volunteering to remove invasives from their area. You can also become more aware of the changing flora around you. It’s never been a better time to be a citizen scientist, so take note and use available apps, such as iNaturalist or IveGot1, to document new plant species observations so you can help researchers make determinations for action. Finally, and certainly not least, make your backyard and landscape a refugia for plant and other species that are on the move or trying to adapt in these new climate conditions. In this era of rapid habitat fragmentation, having a landscape that is biodiverse to support many forms of life, free from invasive plant species, gives plants a big helping hand.
Have questions on plants, hardiness zones or want to transform your backyard into a plant refugia? Contact us and we’ll help you stay informed or create your new native landscape!
