The Science of Spring

March 15, 2017 PLOS Blogs Biodiversity Citizen Science Climate Change Conservation Ecology

I have to admit, at first I didn’t really notice. I live in Virginia, a state in the approximate middle of the east coast of the US. The city I call home is at the foothills of the mountains in the central part of the state, but I work in Richmond, about 70 miles east. Richmond is deep into the piedmont, right on the border of the coastal plain. My commute is not the most extreme climate gradient, but it is almost always warmer in Richmond, and we usually get more snow than they do. And spring, well, there can be a week or more difference between the piedmont and the foothills.

pheno_sarah — From Sarah Scribbles by Sarah Anderson. You should buy her book, it is great: http://sarahcandersen.com/

That’s why initially I didn’t think too much about the dogwood tree along where I walk to my office when it started blooming in early February. I did take a picture and I may have put it on Instagram, but you know who doesn’t do that? But after a few days of late-spring like temperatures and nearly every tree exploding with color, it was hard to deny. Spring had sprung in Virginia.

pheno1 — The dogwood in question in early February (Richmond, VA).

By February 15, everyone had noticed. Jason Samenow of the Capital Weather Gang wrote an excellent piece for the Washington Post heavily circulated in my part of the world. Record February warmth was driving this crazy early spring. But just how crazy is this early spring? Just how do we measure this stuff anyway? And what happens when you get an early spring followed by a slingshot cold snap and with snow to boot?

six-leaf-index-anomaly — Spring leaf anomaly. The dark red indicates areas of early buburst, with some areas as great as 21 days early. It should be noted, that areas around Los Angeles are conversely nearly 21 days behind schedule.

The study of cyclic, seasonal natural phenomena is called phenology. As the National Phenology Network puts it, think of it as “Nature’s Calendar.” Phenological events are not isolated to trees and flowers though. Many male ungulates, such as elk or deer, grow antlers at the beginning of the rut and breeding season each year, many mammals hibernate seasonally to get through the winter, and some birds migrate during the year. Phenological events can be incredibly sensitive to climate change. We are already seeing that the timing of many of these events is changing, though the direction and magnitude of the change differs globally.

From 1982 to 2012, spring budburst (when the leaves first appear) has advanced by a bit over 10 days, while the onset of autumn in the northeast US has pushed back about 4.5 days. No trends were found for other regions. This lengthening of the growing season has profound implications for the ecology of these forests and potentially their ecological evolution. A longer growing season could translate to high carbon storage for increased growth, but higher rates of decomposition and changes in moisture availbility. However, these changes in phenology are primarily driven by increasing temperatures. In a warmer world, some species may simply not be able to survive where they are now, creating a dramatic change in the species composition. And this is without considering changes in precipitation.

Admittedly, it seems odd writing this article in March during a time when our “early spring” has been interrupted by a near-historic blizzard in some places and bitter cold in others. This phenomena, often called a Blackberry or Dogwood winter, is paradoxically perhaps more likely in a warming world. As temperatures warm, early springs like we are currently (or at least did) experience become more likely, however the variance in temperatures is also increasing. These wild swings in temperature combined with early budburst and growth of agricultural crops result in wide-spread crop devastation and severe economic impacts when spring cold snaps occur.

pheno4 — Cold snaps affect species differently. The flowering quince on the left doesn’t mind the freezing temperatures, but after just one night in the cold crushed the blooms on this tree. For reference, both are from the same yard. Also, does anyone know the species for the tree on the right?

So what is being done to track phenology?

My grandparents religiously planned their crop planting and animal breeding by the Farmers’ Almanac. While the accuracy of those assumptions is questionable, it worked for them. Either way, there are other endeavors underway now that don’t specifically look at the phases of the moon–though all good models have room for variable modulation and inclusion.

The PhenoCam network is an ecosystem phenology web camera network that relies on high-resolution digital cameras at established research sites. Images from the cameras are uploaded every thirty minutes to a server, where using simple analysis, quantitative information can easily be gathered from the images. The National Phenology Network runs a project called Nature’s Notebook—a collection over 15,000 naturalists scattered across the nation who, using standardized methods, provide valuable information about plant and animal phenology. There is also Project BudBurst, another citizen science focused project where observations of phenological events and phases are crowd-sourced. The projects and others are revolutionizing the study of phenology. If you have an opportunity to contribute to these or other citizen science projects, please do.