Shelterbelt removals in Saskatchewan, Canada: implications for long-term carbon sequestration

摘要

Shelterbelt agroforestry systems represent an actively managed historical agricultural resource for which farmers are the driving force, and their decisions have long-term consequences. For decades, detailed records were maintained of millions of trees and shrubs planted in shelterbelts on agricultural fields and farmyards across the Canadian Prairies. However, no records were collected regarding shelterbelt removals. This study quantified the length and carbon (C) stocks of all removed shelterbelts in Saskatchewan for the 2008-2016 period, and identified shelterbelt removal trends across five soil zones. Removals were detected using a recently developed integrated GIS and remote sensing approach, and were land-use features that were mapped as shelterbelts in an inventory map in 2008 but were missing in the classified map in 2016. A total of 2491.2 km of shelterbelts were removed, containing 190.7 GgC (1 Gg = 1000 Mg = 1000 tonnes). The majority of C stock removals were in shrub shelterbelts (107.2 GgC; 1676.6 km), followed by deciduous (78.1 GgC; 719.1 km) and coniferous shelterbelts (5.4 GgC; 95.5 km). Medium (2-3 rows) and wide (> 3 rows) shelterbelts had higher likelihood of being completely removed, while narrow (1 row) shelterbelts were only shortened. Removals in the < 50 m length designs were one- to three-orders of magnitude higher than any other shelterbelt length design. Future shelterbelt removal studies could serve to sustain the carbon sequestration effectiveness of the existing and extensive shelterbelt network on the Canadian Prairies in the long term, and to protect an important agricultural resource that took a very long time to establish.