August 2025 marked the culmination of the third census of the Harvard Forest “megaplot,” part of an international effort to track forest change at large scales over time. Over the course of two consecutive summers, 14 research assistants, led by HF Senior Ecologist Dave Orwig, contributed to the the re-census effort, working daily to measure over 70,000 woody stems in the 35-hectare (85-acre) area.
The census is taken every 5 years, and all data are made public. Since 2020, 5,000 new stems have grown to at least 1 centimeter in diameter. Those sapling newcomers include over 1,000 hemlock trees and over 800 mountain laurel and black birch stems.
This census also documented over 11,800 dead stems–with almost 5,000 of them being eastern hemlock that succumbed to the invasive insect, the hemlock woolly adelgid (HWA). Altogether, more than 8000 hemlock have died in the plot since initial measurements in 2014.
Norway spruce and red pine plantations that were established by Harvard Forest students in the early 1900s have been steadily dying as well, leaving very few of either species remaining in the study area.
- Learn more about our role in the international ForestGEO project
