Not Blooming Like They Used to: Plant Species and the Climate

At the start of each spring semester, many of us are excited to watch the colors in our landscape change as flowers are soon to start their blooming cycle – but these cycles are not the same as they were before. In the past decades, these cycles have been tremendously affected by the changes in the climate. Such changes are dangerous for the way plants bloom, survive, and reproduce – constituting one of the most conspicuous ecological effects of climate change around the globe.

Dr. Matthew Austin is a Postdoctoral Research Associate in the Living Earth Collaborative as part of the Department of Biology at Washington University in St. Louis. He studies how climate change affects the time of year that plant species bloom. His research uses flowering records to not only contribute to the documentation of the changing flowering time caused by a warming climate, but also to how those changes affect the ways plants interact with one another and how that can have cascading effects on the survival, reproduction, ecology, and evolution of plant-pollinator communities.

Broadly, plants are very sensitive to climate change, and flowering time is readily observable, which is why the topic is so crucial to the understanding of the effects of Climate Change.

“We can think of plants as indicator species for how climate change is affecting ecology.”

The relationship between Climate Change and flowering time is very direct. Climate Change has caused average global temperatures to rise, which in turn forces the spring season to start earlier than it has in the past. In parallel with the premature start of the spring season, flowering also starts earlier in the year. This relationship is easier to document than most climate change effects, so if we document changes to flowering time in the spring, then it’s likely that climate change is having cascading ecological effects, which might not be so obvious as flowering time, at least to the human eye.

There is no lack of flowering data in Dr. Austin’s research – and that is due to his partnership with the Missouri Botanical Garden. In one of his major projects, he uses long term records from the Shaw Nature Reserve, especially the collections from 1938 to 1941 and from 2009 to 2012. These records specify which plants bloom at which dates in the year, which allows comparisons of the flowering pattern from the early 20th century and the early 21st century – then we can link changes in flowering time to climate change by pairing flowering records with historic climate data. Since the research can track how much each flower’s blooming cycle has changed by degree Celsius of global warming, we can specifically say if the changes are due to climate change or not.

Moreover, Dr. Matthew Austin’s studies show that not every species is affected in the same way. A prominent example is bloodroot (Sanguinaria canadensis), a species that has shown very little change in its flowering time over the century. Being one of the first flowers to bloom in the spring, bloodroot now faces competition from flowers that are blooming earlier than usual, having the highest increase in co-flowering overlap among peer species. This type of occurrence is becoming increasingly common, and the competition created between flowers blooming at the same time can affect their reproductive cycle, and even potentially drive species to extinction inside the community.

“There’s a real possibility that the changes we’re seeing could be irreversible. bloodroot and some other plants are facing greater competition than they used to, which could decrease genetic diversity in the species and ultimately drive these species to extinction.”

Ecology is a highly interconnected field, and it can be hard to predict what downstream effects will happen when you remove one species from an entire community. Thinking about how ubiquitous the effects of climate change are on plants, it’s quite likely that not only one or just a select number of species will be affected.

Looking forward, Dr. Austin sees potential not only in the flowering records, but also through other biological archives of the Missouri Botanical Garden. Use and analysis of these archives has an immense potential to answer questions related to climate effects on plants. Moreover, Dr. Austin understands that his work must serve as a warning about the changing climate of the planet, and he believes there are many different ways we can tackle the climate crisis – which will in turn restore healthier flowering cycles. From his experience, he emphasizes nature-based climate solutions, which involve conserving, restoring, or better managing ecosystems to remove carbon dioxide (CO2) from the atmosphere. Moreover, he argues that there are immediate ways to respond to the threat of extinction of plant species due to the changes in flowering, such as ex-situ conservation, a proactive form of conservation where the plant is stored if you identify that the species is threatened with distinction.

Personal website: https://matthew-w-austin.weebly.com/
Relevant publication: https://doi.org/10.1002/ajb2.16021