Abstract

ABSTRACT


Topic: Moose and forestry


SEVENTY-FIVE YEARS OF BROWSING BY MOOSE: LESSONS IN FORESTRY FROM A MODEL HERBIVORE

Christer Kalen1, Märtha Wallgren2, Jonas Bergquist3

  1. Swedish Forest Agency, Bryggaregatan 19-21, 501 13 Borås, Sweden
  2. Skogforsk, Forestry Research Institute of Sweden, Uppsala Science Park, 751 83 Uppsala, Sweden
  3. Byhult 3, 571 97 Forserum, Sweden

Abstract
Since the 1950s, scientists in Sweden have studied moose (Alces alces) browsing damage on Scots pine (Pinus sylvestris), enhancing our understanding of its impact on silviculture. Early studies not only established a classification system for browsing intensity but also recognized its influence on stand structure and tree species composition. In the 1960s, changes in moose and forest management led to an exponential increase in the moose population. By the 1980s, it is estimated that Sweden harvested more moose than all other countries combined. However, declining forage availability, combined with sustained high harvest levels, eventually caused a population drop. Despite this, forest damage remained a concern, prompting calls for more intensive reductions in moose numbers. In response, the Moose Browsing Inventory was launched in 2000, initially focusing on damages affecting timber quality. By 2010, a long-term study revealed that heavily browsed stands produced only 30% of the volume of fenced stands, highlighting the impact of browsing on forest growth. To better balance a high-yield moose population with sustainable browsing levels, a new national moose management system was introduced in 2012. Since 2015, browsing damages have been systematically monitored across all 130 moose management areas. By 2019, the National Forest Agency estimated that browsing-related losses accounted for approximately 5% of Sweden’s annual forest growth. To mitigate damage, foresters increasingly planted Norway spruce, particularly in southern Sweden. However, this strategy had unintended consequences. A severe bark beetle outbreak caused a decline in the species’ popularity among forest owners. Additionally, dense spruce forests reduce the availability of field vegetation for moose and other deer species, prompting hunters to advocate for forestry practices that enhance browse availability. Today, scientific debate continues regarding the relationship between moose density and pine browsing damage. Large-scale analyses across management areas often fail to capture the true nature of this relationship within individual areas, necessitating a more nuanced approach. Moving forward, a deeper understanding of the mechanisms driving browsing damage—along with the complex interplay between moose density, browsing pressure, and resulting damage—will be important for refining management strategies and ensuring sustainable coexistence between moose and forestry.