Climate Change Impacts on Maple Syrup Yield in Nova Scotia, Canada

Maple syrup yields have constantly been declining, which is of major concern to maple syrup producers in Nova Scotia, Canada. Climate change is suspected to contribute to this decline; nevertheless, no specific studies have been conducted in Nova Scotia to ascertain this. Furthermore, the industry faces the challenge of identifying the optimal start date of the sap flow to maximize sap yields and subsequently increase economic returns. Sap flow is a consequence of the interactions between the tree’s physiology, environment and weather; and our knowledge of the influence of weather on maple syrup in NS is very limited. Owing to this gap, no indicators are currently available to scientifically assist in projecting tap date or harvest decision processes. To address these issues: (i) assessed the climate change scenario in NS, (ii) evaluated link(s) between the climatic factors and syrup production, and (iii) modeled the relationships to predict syrup yield and sap flow dates. Historical weather data from various weather stations was collected from Environment Canada and the Maple syrup production data was collected from growers across NS. Changes in the weather parameters for mean temperature and effective growing degree days (EGDD) were assessed against the average maple syrup records from 1978-2013. We found that mean annual temperature has increased by 1^oC in the last 15 years. This increase has translated into an increased average EGDD of 125 days. The implications on the maple tree growth were multi-faceted and negative in relation to syrup yield. When historical syrup yields and EGDD were regressed, it was evident that the decline in syrup yields (0.65 to 0.33 L/tap/yr) coincided with the increase in the EGDD in NS. Simultaneously, during this period, the start date for the sap flow has started approximately five days earlier. However, the length of tapping season remains unchanged. These trends indicate a negative effect of climate change on NS maple syrup production. Over 108 weather parameters were screened for their relationship with syrup yields, only six of the weather parameters strongly correlated with syrup yields and three weather parameters correlated with the start date of the sap flow. A neural network-based syrup yield model was constructed with these parameters to predict syrup yields and start date of sap flow. The syrup yield model exhibited strong potential to predict the syrup yields and start date; however, its ability is limited owing to the small size of training data currently available.