From South to North: Climate Change Impact on Plants

This summer I went from Manitoba’s southern-most border all the way to its northern one within just a week. I was fascinated to see how differences in climate had influenced the plant communities. The massive trees of the south give way to nearly treeless tundra in the far north. But despite being separated by over 1,000 kilometers, both places had something in common: climate change was beginning to impact the plants.

In early August, I drove to Buffalo Point First Nation to search for rare plants, with the permission of the community. Buffalo Point is in the extreme southeastern corner of the province. Many plants reach their northeastern limit in that part of the province, including Interrupted Fern (Osmunda claytoniana).

In addition to hiking the trails there, I travelled by boat down the Reed River with two Indigenous guides. I was looking for rare plants that grow on shorelines. Alas, they were not there. Due to the heavy snow and rain this year, the water level was higher than my guides had ever seen in their lives. The water extended right into the forest, killing some of the waterlogged trees and flooding once productive beds of Wild Rice (Zizania palustris).

A week later, I was on a plane to Churchill to search for rare plants in that part of the province. Once again, I visited a river that was swollen beyond its usual level: the Churchill River. My Indigenous guide commented that the normal shoreline vegetation was completely covered by water. But it wasn’t just the river vegetation that was being impacted, either.

Another Indigenous person I met told me that her 70-year old grandfather had witnessed huge changes in the tundra around Churchill in his lifetime. Tall shrubs, like Silver Willow (Salix candida), were much less common in the past. These tall species are now increasing in abundance, as they can out-compete the short, tundra vegetation when temperatures are warmer (Mekonnen, 2021).  With continued warming, this “shrubification” will likely continue, completely changing the plant communities in the far north.

Short, tundra plants like White Mountain Avens (Dryas integrifolia), shown above in fruit, may become rare in Manitoba, as climate change increases arctic temperatures and thaws permafrost. © Manitoba Museum

The new map in the Museum’s Prairies Gallery shows the location of now extinct wetlands like the Great Hay Marsh. © Manitoba Museum

You may have heard the old saying that “nature abhors a vacuum”. To understand this expression, you probably won’t need to look any farther than your own lawn. Although lawns may start out as monocultures of Kentucky Bluegrass (Poa pratensis), they never stay that way. Inevitably, species like Common Dandelion (Taraxacum officinale) show up, prompting a flurry of weeding and spraying of herbicides. We are told by lawn care companies that “healthy lawns won’t allow weeds to grow” but that statement is simply not true. Just look at any wild ecosystem in the world. Is it a monoculture with just one species? No, there are always many species. Weeds eventually invade lawns because monocultures are NOT natural. Ecosystems want to return to a natural state.

Native prairie ecosystems are natural polycultures: systems with many plant species. © Manitoba Museum

But why did lawns even become popular in the first place? In Europe, in the 16th century, wealthy landowners began growing lawns to flaunt their status. They didn’t need the land to grow food, they were rich enough to grow completely useless grass on their property instead! As the European middle class began to grow, they also aspired to demonstrate their wealth by growing at least small patches of lawn, if they could. This Western appreciation of the lawn aesthetic still remains with us today, but there are signs that its time is up. Concern about the impact of lawn care pesticides on human health and vulnerable pollinators has prompted many municipalities to enact bans on these chemicals.

Further, the popularity of polyculture lawns is experiencing a resurgence. Polyculture lawns more closely mimic a natural ecosystem by including both grasses (ideally, low growing native species like Blue Grama a.k.a. Bouteloua gracilis) and low growing, broad-leaved plants, such as clover (e.g. Trifolium), native violets (e.g. Early Blue Violet a.k.a. Viola adunca), pussytoes (Antennaria spp.) and yes, maybe even some dandelions. Broad-leaved plants provide pollinators with food, and some species, like legumes, naturally add nitrogen to the soil, reducing the need for fertilizers. In shady areas where grass won’t grow well anyway, ground covers of taller, native plants like Ostrich Fern (Matteucia struthiopteris), Western Canada Violet (Viola canadensis) and Canada Anemone (Anemone canadensis) are great alternatives.

Trying to keep your lawn “weed” free is like running on a treadmill: you spend lots of energy but you never get anywhere. Why not embrace the diversity of plant life, and save your money and back-breaking labour for something else?

When I tell people I am writing a book that describes all of the plants that grow in Manitoba, they are often incredulous. “Don’t we already know how many plants species there are in Manitoba” they ask. Sadly, the answer is no. 

Believe it or not, botanists documented and collected two flowers that were not believed to grow in the province, for the first time ever in 2021. White Avens (Geum canadense) and Tawny Cottongrass (Eriophorum virgatum) grow in northern Minnesota and western Ontario. However, they had never been scientifically collected in Manitoba before. These species join 268 other species of vascular plants that have been scientifically collected since the publication of the “Flora of Manitoba” book in 1957. 

Further, the Royal Alberta Museum’s moss specialist, Dr. Richard Caners, also recently collected 34 species of moss that had not yet been officially documented in Manitoba. So, on average, nearly five new plant species have been added to our provincial list of flora each year for the last 65 years. 

You don’t even need to do field work to find new species! In the last several years, Museum volunteers discovered several previously unknown species in the Museum’s collection of pressed, dried plants. These preserved plants, called “herbarium specimens”, officially confirm the presence of species in the province. Along with the specimen, data on when and where it was collected are provided. The Manitoba Museum alone has over 50,000 of these herbarium specimens. What makes them so valuable is that they can be examined by experts without having to travel back to the area where the plant was collected. Scientists use them to determine the rarity of species, and understand how the climate has changed over time, among other things. 

One of my jobs as Curator is to make sure that all our plants are identified correctly.  This requires studying the  most up-to-date scientific research. While examining specimens of Yellow Evening-primrose (Oenothera biennis), my volunteer and I determined that two specimens were, in fact, a species that was not confirmed to be in Manitoba until very recently: Oakes’ Evening-primrose (O. oakesiana). 

So why are scientists still finding new plants in Manitoba? Part of the reason is that scientific field collecting is poorly funded. There is a widespread perception that Canada is well-explored biologically, and that there is nothing unusual left to find here. So, such expeditions are typically deemed unimportant and not funded. Another reason is that Manitoba has relatively few roads in the northern ¾’s of the province. This makes it very difficult, and expensive, for scientists to visit pristine areas where rare plants may grow. 

When I say that a plant species is “new” to the province, what I mean is that no scientist had collected, preserved and stored a sample of that species in a registered herbarium.  This does not mean, however, that no one has ever seen the plant. Someone may have seen it, but not realized that it was anything unusual. 

As the stewards of large tracts of undisturbed land, Manitoba’s Indigenous peoples are likely aware of the presence of plant species that professional botanists do not know much about. The Manitoba Museum is beginning to work with Indigenous peoples to incorporate their knowledge on the distribution and rarity of the province’s plants into our database. 

When most people think of plants, they typically picture flowers: cherry trees in bloom, colourful tulips and exotic-looking orchids. This is because 90% of all living plant species are flowering plants (i.e., angiosperms). But when dinosaurs first evolved 225 million years ago (mya), flowers were nowhere to be found.

The first land plants did not produce seeds; instead, they reproduced using spores. Like amphibians, they needed water for reproduction, which restricted them to habitats that were moist. These spore-producing plants included mosses, liverworts, club mosses, horsetails, ferns and several, completely extinct plant groups called Rhyniophytes and Zosterophylls. When the first dinosaurs evolved in the Triassic Period (252-201 mya), spore-producing plants, like tree ferns and human-sized quillworts (e.g. Pleuromeia), were common (Palmer et al. 2009). Although these sorts of plants still exist today, their ancestors looked much different than the ones we are familiar with.

Above: Many modern flowering plants, such as Early Yellow Locoweed (Oxytropis campestris), coevolved with pollinating insects, such as bumblebees (Bombus). © Manitoba Museum

So, when you visit the Ultimate Dinosaurs exhibit at the Manitoba Museum during summer 2022, remember to look closely at the murals behind the dinos. They accurately portray the kinds of plants that supported those ancient creatures so long ago.

Mural art from the Ultimate Dinosaurs exhibit showing ancient vegetation communities. © Ultimate Dinosaurs Presented by Science Museum of Minnesota. Created and Produced by the Royal Ontario Museum. Mural Artist: Julius Csotoyi

References

Benton, M.J., Wilf, P. and Sauquet, H., 2022. The Angiosperm Terrestrial Revolution and the origins of modern biodiversity. New Phytologist, 233(5), pp.2017-2035.

Condamine, F.L., Silvestro, D., Koppelhus, E.B. and Antonelli, A., 2020. The rise of angiosperms pushed conifers to decline during global cooling. Proceedings of the National Academy of Sciences, 117(46), pp. 28867-28875.

Cui, D.F., Hou, Y., Yin, P. and Wang, X., 2021. A Jurassic flower bud from the Jurassic of China. Geological Society, London, Special Publications, 521.

Palmer, D., Lamb, S., Gavira Guerrero, A. and Frances, P. 2009. Prehistoric life: the definitive visual history of life on earth. New York, N.Y., DK Pub.