By: Humza Yaqoob, Columnist
Data collected through long-term remote sensing shows us that the responses from plants to seasonal changes have been occurring two to three days earlier in the spring and 0.3 to 1.6 days later in the fall per decade for the past 30 to 80 years. This change has resulted in an extension of the growing season and increased productivity in both terrestrial and aquatic ecosystems. Year-to-year variability is still highly variable, but the overall change in seasonal trends for plants will ultimately reshape ecosystems.
While the increased productivity and longer growing season might sound good at face-value, these changes come at a cost. Although northern latitudes will have a higher potential for crop production, increased warmth in already warm areas may cause a slight decrease in crop yields. The fast rate of climate change won’t allow trees to adapt to new conditions — different tree species may adapt differently, altering inter-species competition, and the latitudinal range of some species may occur at the expense of restricting the range of others. The rapid disruption of ecosystems can increase vulnerability to invasive species and cause the decoupling of pollination relationships.
Although the advancement of spring represents a larger change, the delaying of fall has some significant implications. Chlorophyll does not break down as well during extended periods of warmth without cold night times, causing the color of leaves to be relatively dulled when the transition to fall does occur. Increased likelihood of wind and precipitation associated with climate change has increased the potential for leaves to be removed before they change color. As atmospheric carbon dioxide levels rise, trees stay green longer as they use that carbon dioxide to continue photosynthetic production. In doing so, they delay the setting of buds to prepare for winter. Too long of a delay would increase plants’ vulnerability to frost and other winter weather events. Fall is not just happening later than it has been over time, it is starting to look different as plants respond to this change.