How monitoring phenology helps us understand climate change

Plant and animal species are changing in a variety of ways — some species’ life cycle events are changing dramatically, others aren’t. This variety of responses, which species are changing and which are not, is really important in knowing which are functioning well and which are in trouble. That information could affect the practices of farmers, resource managers, and others. Currently, we don’t have enough data and therefore are lacking knowledge about these changes for many important species.

Climate scientists have found that changes in the historical timing of plant and animal phenology is one of the most sensitive indicators of the local effects of global climate change. Scientists, naturalists, farmers, gardeners, fishermen and many others have been recording their observations of seasonal phenology changes for centuries. A patchwork of records exists in notebooks and logbooks, ledgers and bills of sale. Matching historical observations with more recent ones has allowed climate scientists to identify shifts in long-term phenology trends that closely match our records of Earth’s warming temperature. Phenology records can help scientists fill in gaps and verify trends in other sources of data to get a more complete picture of the local effects of global climate change. They also help scientists predict changes that may come in the years and decades ahead, which will help all of us understand, respond, and prepare for our changing climate.

One example of the importance of phenology recordkeeping can be found just to our south. In the 1850s, naturalist and philosopher Henry David Thoreau recorded the plant species and flowering times that he observed near Walden Pond in Concord, Massachusetts. Today, his careful work allows scientists to compare current species and flowering times with those in Thoreau’s day, and find that plant flowering dates have shifted by as much as three weeks earlier in response to Concord’s warmer spring temperatures over the past 160 years. Species without flexible flowering times, such as lilies, orchids, and roses, have not been able to adjust to the warmer environment as well as those with flexible flowering times, including non-native and invasive species (Willis et al, 2008; Willis et al, 2010). This type of information allows today’s climate scientists to learn from the past, understand our current situation, and make plans for the future. Without Thoreau’s journals, it would not have been possible to make this discovery.

Phenology scientists’ research on Thoreau’s journals and other historical records has also shown us that plant and animal species are responding to climate change in a variety of ways — some species’ life cycle events have changed dramatically, while others have remained fairly constant. It is important to watch and record this variety of responses by monitoring phenology, because it helps us understand which species are capable of adapting to our changing climate, and which ones may be in trouble. Information collected through programs like Signs of the Seasons could help farmers, gardeners, fishermen, resource managers, and others understand how the species they rely on are changing, and predict threats they might face in the future. Currently, we don’t have enough data about these changes for many important species in Maine, but your participation in this project will help fill that gap.