“In Search of Thoreau’s Flowers” explores one small example of the mass extinction that has been occurring since the Great Acceleration, when humans became dominant forces shaping the biosphere. For most plant species, we do not know precisely how climate change has altered their fates because scientists have very little data from before climate change on ecosystem processes that are governed by temperature. This lack of data severely limits how much scientists can learn about the complicated changes associated with shifts in climate and simultaneous urban development, air pollution, pesticide use, and spread of invasive species.
One phenomenon that has clearly shifted as a result of climate change is the timing of plant life history events in a given year, such as bloom, leaf-out, and fruiting. In the temperate and boreal regions of the world, plants now bloom earlier than before climate warming because their development is contingent on temperatures, which have now risen by almost a degree Celsius on average worldwide. The timing of plant bloom has important ecological effects; it can determine how well plants are pollinated, how much they are fed on by plant-eating insects, and how much light they have access to relative to their nearby plant competitors.
While plants in general flower earlier than prior to climate change, shifts in flowering are asymmetric across the plant family tree. We know this because of Henry David Thoreau.
As he meandered through what would later be known as Thoreau’s Woods in the mid-1800s, he noted which plant species were flowering. This was primarily a spiritual and not a scientific exercise, although Thoreau had studied botany at Concord Academy as well as at Harvard University. However, Thoreau’s ‘data’ on flowering have fueled critical discoveries. Recently, scientists transcribed records from Thoreau’s diaries describing bloom timing in springs that predated climate change. In a now classic study, these same scientists revisited Thoreau’s Woods to collect the data Thoreau (accidentally) recorded, but for modern plants.
They found that, in general, plants flower earlier now than in Thoreau’s time. However, plant families are differentially sensitive to temperature. Some families bloom earlier in warmer springs and winters, while others do not. In a later study, scientists showed – with similar plant abundance surveys from before and after climate change – that the plant families that did not advance their flowering during the year as a result of climate warming tend to be in decline.
“In Search of Thoreau’s Flowers” uses the data underlying these studies about plant abundance, decline, and loss to artistically visualize the botanical winners and losers of climate change.