As our climate changes, we might expect to see some familiar plants and animals in our local environment replaced by new ones. That’s according to Bill Morris from Duke University in Durham, North Carolina, who recently published work studying shifts in where mountain plants live in top science journal Nature. “Species will likely be found in different places than where they are found now, creating new combinations that did not interact in the recent past,” he told Simple Climate. “What the consequences of these new interactions will be are hard to predict, because it is difficult to study interactions that don’t currently exist.”
Together with Daniel Doak at the University of Wyoming, Morris studied two tundra plant species whose habitat extends south from the Arctic. Higher global temperatures are expected to make conditions for the moss campion and alpine bistort better at the northern end of their geographical ranges. By contrast, at the southern end higher temperatures might be expected cause the plants to decline. Consequently their southern range limit should move northwards, but Morris and Doak found that in fact this had not happened – at least not yet.
Morris explained that the question of whether species’ ranges are spreading, or if it’s more common for the range to stay the same size, but move, remains unanswered. “We have much better evidence that species such as butterflies and birds are shifting toward the poles and to higher elevations, because these species are more often noticed by amateur naturalists, and because they likely move faster than do plants,” he said. “But we do know that many plants in Europe, where historical information about plant distributions is better, have moved to higher elevations over the last century.”
Plants as canaries
This lack of knowledge helped to make Morris’ recent study more important. “Tundra plants such as moss campion and alpine bistort don’t represent a large fraction of the mass of plants on Earth, so they don’t play as much of a role in storing carbon as, for example, trees,” he conceded. “However, because they are suited to living in cold environments, they may serve as useful ‘canaries in the coal mine’, providing early warning of climate change effects before those effects are observed in other, more abundant plants from warmer environments.”
However, the study was designed to provide more than just basic data about where plants had been found, and instead sought to look in depth at how climate change had affected these two quite distinct species. “To address other questions, we had been studying the moss campion in Alaska’s Wrangell mountains for 6 years when we began our study across North America,” Morris explained. “We chose to add alpine bistort because its growth form is different than the moss campion.”
Doak and Morris had to painstakingly tag and catalogue the plants themselves as well as the bulblets they drop in reproduction, a job that has enviable aspects – and some distinctly unenviable ones. “Mountain habitats are certainly nice places to work sometimes,” Morris said. “But when it is 33ºF (0.5ºC) and raining or snowing on Alaska’s North Slope counting small seedlings, we might sometimes dream of being on a tropical beach. Also, because these are low plants, counting and measuring them means working on hands and knees for weeks on end. But then again, hiking up the mountains to where these plants live does keep you in good physical shape!”
The researchers’ cataloguing allowed them to assess the “vital rates” of the plants – survival, growth and reproduction – at four different locations. From one perspective perhaps the plants’ extended range stems from their hardiness. “Both have proven to be very long-lived plants,” Morris said. “For example, some moss campion plants can attain an age of over 200 years.” The detailed analysis showed that some vital rates are suffering due to climate change, but others are benefiting, which is why the plants’ geographical ranges are not currently shrinking. Yet ultimately, continued increases in temperature can be expected to adversely impact all vital rates, Morris underlined. “Our study shows that species can show little response to climate change for a long while, and then suddenly shift as a climatic tipping point is surpassed,” he said.
Morris explained that global warming’s effect on location could have a serious impact on some organisms. “With more greenhouse gases in the atmosphere, we will have a warmer world with altered patterns of precipitation,” he said. “Both of these changes will alter where each species can live.” Morris explains that such altered locations have been seen in the past, and more recently some have already been seen over the last century. Based on the fates recorded for past species some, but not all, will be able to respond to the changes effectively, Morris underlined. “Some species may be able to make the shift to the new locations, or evolve to tolerate new conditions where they are not found, but others may not, and will face extinction in the future climate.”
Although altered locations may be most obvious in some ways, Morris notes that other effects of climate change on plants could be even more important. “Perhaps even more noticeable than shifts in species’ geographical ranges so far is changes in the timing of life events such as plants flowering or birds migrating,” he said. “A big concern is that, if these changes are not synchronous, flowers may be out of sync with their pollinators, birds out of sync with the insects they feed on.”