Weather, climate change and the urban forest

 In Blog, Tree Pittsburgh

The weath­er in Pitts­burgh is nev­er con­sis­tent. From Snow­mage­den to the Polar Vor­tex, our win­ters over the last six years have pro­vid­ed us with a new vocab­u­lary. While sum­mer weath­er has­n’t pro­vid­ed any new words, it has been just as unpre­dictable: from sum­mers where we had to do vir­tu­al­ly no water­ing of trees to sum­mers where we could­n’t water all of them, we’ve had some dras­ti­cal­ly dif­fer­ent cli­mates. Weath­er is the state of the atmos­phere at a spe­cif­ic place and time, and cli­mate is the weath­er con­di­tions in an area in gen­er­al or over a long period.

The warm win­ter this year caused Direc­tor of Urban Forestry Matt Erb’s Cro­cus ver­nus “Pick­wick” to flower March 8. While plen­ty of data and sta­tisics are record­ed dai­ly to pro­vide weath­er and cli­mate analy­sis, quan­ti­fy­ing the impact a chang­ing cli­mate has on plants is more dif­fi­cult. For exam­ple, a sea­soned gar­den­er may notice that their Brus­sels sprouts did­n’t grow one year due to poor weath­er or that their figs failed to ripen due to a short­er grow­ing sea­son. Some gar­den­ers even keep jour­nals not­ing flower or har­vest times.

The prac­tice of track­ing sea­son­al nat­ur­al phe­nom­e­na is known as phe­nol­o­gy. By mak­ing obser­va­tions of the nat­ur­al world around us (espe­cial­ly plants) and record­ing this data in a data­base, the impacts of cli­mate change on plants can be studied.

Over the last four years. Matt has used his smart phone to take pho­tos of the first Cro­cus flow­ers that bloom in his gar­den. In 2013, it was March 29. In 2014, March 31. In 2015, flow­ers bloomed April 1. This year, they bloomed three weeks ear­ly on March 8. While there is typ­i­cal­ly a week dif­fer­ence between blooms on the sun­ny side of his gar­den vs. the shady side, the dif­fer­ence this year was only two days. These flow­er­ing times also close­ly relate to the flow­er­ing of Mat­t’s Cor­nelian cher­ry dog­wood (Cor­nus mas). Anoth­er obser­va­tion of 2016 is that no hon­ey bees have been present on these flow­ers, which may or may not be tied to the ear­ly blooms but cer­tain­ly illus­trates the poten­tial impacts of cli­mate change and the whole ecosystem.

While Mat­t’s casu­al back­yard obser­va­tions show this year is an anom­aly, over­all flow­er­ing times are becom­ing ear­li­er. Longterm phe­no­log­i­cal data has shown many flow­er­ing plants that Hen­ry David Thore­au observed at Walden Pond are flow­er­ing approx­i­mate­ly three weeks ear­li­er today than in Thore­au’s time. Phe­nol­o­gy can also be used to record obser­va­tions of insects, mam­mals and oth­er liv­ing crea­tures, help­ing to paint a larg­er pic­ture of how the tim­ing of nature and cli­mate is chang­ing and what impact that may have on the larg­er ecosystem.

To learn more about phe­nol­o­gy in your back­yard, vis­it the USA Nation­al Phe­nol­o­gy Net­work.

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