In spring we see a lot of changes taking place as temperatures warm heading into summer. Recurring events in the life cycles of many organisms are influenced or determined by changes in the weather. Phenology is the study of these cyclic and seasonal changes in plant and animal life in relation to what is going on with current climate changes. An example is a series of changes that take place in plants throughout the year starting in spring with budburst, leaf-out, flowering, fruit ripening, leaf-coloring, and leaf-fall. All of these stages in the life cycle of a plant are determined by what is happening with the climate where that plant is located.
The history of phenology dates back to the mid-1700s. In the late 1800s, fanciers in England made phenology one of the first citizen science pastimes and attracted over 600 observers. Results of plant changes were kept by the Royal Meteorological Society of Great Britain until the late 1940s, when the activity simply fell out of favor. It was restarted in England in 1998, and continues today. Robert Marsham, considered to be the founder of modern phenology, was a naturalist living on his country estate in Norfolk, England. In 1936, he started writing “Indications Of Spring” a publication of his phenology notes recording 27 springtime changes. Some of those included first leaf, flowering dates, and first sightings of butterflies and swallows. He devoted over sixty years to this work. After his death, further generations of his family added to it well into the 20th century.
Here is an example from observations of springtime events in oak trees. In the last 250 years in England, overall temperatures have risen an average of 1.5˚C. First leaf-out of oaks in spring is occurring eight days earlier, and bud-burst is happening eleven days earlier. Thousands of insects that depend on oak trees for food and shelter are now emerging earlier due to these changes. Migrant birds returning to England to mate and raise young depend on the emerging insect populations for food at the same time as young birds are born. The data indicates that returning birds have not been able to keep up with these timing changes. As a result, babies are born too late, after other predators have reduced one of their major food sources, negatively affected the bird populations and the entire food chain.
There are several published studies of plant and animal observations including climate data, made over long periods. Analysis of this data reveals the progress and changes in the annual natural calendar. Interactions between plants and animals are vital to the survival of individuals and whole species. Much of this knowledge comes to us from herbaria records documenting these ecological changes over time. Collections include dried specimens, field notebooks, and journals recording observations and hypothesis fitting the facts into known history of the moment. Knowledge of phenology and understanding the timing of events provides critical data for habitat management. Applications of phenology include management of invasive species and forest pests, predictions of human health-related events, such as allergies and mosquito season, optimization of when to plant, fertilize, and harvest crops, understanding the timing of ecosystem processes, such as carbon cycling, and assessment of the vulnerability of species, populations, and ecological communities to ongoing climate change.
The USA-NPN, National Phenology Network, was established in 2007 to collect, store, and share phenology data and information. It provides a place to assemble long-term phenology datasets for a many species across the U.S. Data is used to create models from historical changes. These models, coupled with current observations, help us understand how different species respond to changes in climate over time in specific habitats. This type of study can be used to determine the extent to which species, populations, and communities are vulnerable to ongoing and projected future changes in climate.
Nature’s Notebook is the USA-NPN program allowing professionals and volunteers to record long-term observations of plant and animal life changes. If you would like to try a fun activity, and be part of a large network of observers and gain a better understanding of what you are seeing in your own neighborhood, consider becoming an NPN volunteer scientist. There are lots of resources available to assist you in making observations and in learning about nature. USA-NPN general information can be found at https://www.usanpn.org/home or become an observer by signing up at: Natures Notebook (https://www.usanpn.org/natures_notebook).
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