Every year, I like to record the first flower I see blooming. This year, since I live in Southern California, it was a prickly pear cactus in mid-January. When I lived in a colder environment, Northern Utah, I would usually see Penstemon flowering in late May. The environmental conditions of an area play a huge part in determining when a plant flowers, and the timing of when plants flower, called phenology, is changing due to climate change.
At Mount Rainier National Park, located in the Cascade Mountains outside of Seattle, and other alpine environments, flowering timing is related to snow melt. And the number of visitors to the park and the timing of those visitors is related to flowering. Everything is connected. Ian Breckheimer and colleagues from Harvard University were interested in understanding how plant flowering and human visitation were affected by seasonal and annual variations in climate. Historically humans tended to visit the park during peak wildflower season, but as wildflower season shifts are humans also changing their behavior?
Using publicly available photos on the popular photo sharing site, Flickr, the researchers were able to track the changing patterns of wildflower blooms and snow melt using photos that are geotagged at Mount Rainier National Park. The abundance of photos geotagged is also representative of the number of visitors at that park at the time the photo was taken. Based on the photos of wildflowers, Flickr unique users per day, and National Park Service visitor records, the researchers were able to link ecology with human behavior and look for trends.
They found that both flowering and visitors were sensitive to changes in climate. For every ten days earlier snow melt, human visitors arrived about 5 days earlier and flowers bloomed about 7 days earlier. This led to a longer season of human visitation, especially since much of the park is not accessible when covered in snow. However, earlier snowmelt led to a shorter period of flowering. This led to a phenological mismatch.
This term is often used to describe what happens when a plant flowers at a different time than when pollinators are active, but it can also be used to describe what happens when the wildflowers people want to see are not active when people are there to see them. In 2015, when snow disappeared very early at Mount Rainier, this led the match between visitors and flowers to decrease by 35% compared to a late snowmelt year. When snow melts earlier, people will have a lower chance of seeing the iconic wildflowers.
These types of mismatches are more common when the two groups are driven by different environmental cues, as is the case here with humans and plants. Plants don’t really care if a human is there to photograph them and are driven by environmental cues such as more water from the melting snow, longer days, and warmer weather. And humans often don’t plan their trips by checking on the phenology of wildflowers. Out of town visitors are common at Mount Rainier and they wouldn’t know when the plants are flowering and may miss peak bloom (this has happened to me at many parks unfortunately). Additionally, there are restrictions on what roads can be open in the park and when to keep visitors safe, this poses an additional barrier and amplifies the mis-match. As the climate continues to warm and National Parks continue to maintain high visitation rates, the frequency of these mismatches will increase both at Mount Rainier and around the world.
For Mount Rainier this is a problem because people value the wildflower meadows within the park and without them and more importantly, without people seeing them and wanting to conserve them, the park may eventually lose support for conservation and preservation measures. There is not much we can do to change the plant’s phenology but there are things we can do to change our own. The authors suggest that shifting road opening times to match the snow melt conditions and providing potential visitors with information about the snow pack and wildflowers could alleviate some of the issues causing the mismatch.
These are small steps we can take to change human behavior in the short term to increase visitor’s chances of seeing peak wildflower blooms. However, climate change is threatening the survival of these wildflowers and their ecosystem and highlights the need for humans to drastically change their behavior to prevent future mismatches in the future.
Source: Brekheimer et al. 2019. Crowd‐sourced data reveal social–ecological mismatches in phenology driven by climate. Front Ecol Environ 2020; 18( 2): 76– 82, doi:10.1002/fee.2142