Forest Management Impacts on Tree Species Diversity: Effectiveness and
Costs in Light of a Beetle Epidemic
Abstract
In western North America, a recent epidemic of mountain pine beetle
(Dendroctonus ponderosae) caused widespread forest mortality. This
outbreak was in part due to the changing climate, and damage from pests
and diseases is expected to increase in the future. To learn from this
event, we used a historical retrospective approach to evaluate
business-as-usual and alternative management strategies effects on tree
species diversity. The insurance hypothesis proposed that ecosystems
with greater species diversity will have greater productivity due to the
buffering effect against natural disturbances. Therefore, we
hypothesized that management strategies to increase diversity before the
beetle outbreak could result in higher growing stocks, harvest rates,
and net present value. The assessment was based on simulation modelling
of a 1.1 million ha landscape in British Columbia, Canada for
1980–2060. We applied different strategies to affect diversity: harvest
more of the most dominant tree species, planting more diverse species,
and increase natural regeneration. The most aggressive strategy resulted
in higher diversity and growing stocks, higher harvest rates, and
higher, more consistent net revenue over time than the business-as-usual
strategy. However, the strategy that only employed a diversity of
planting negatively affected those indicators. Thus, we have identified
limitations to what management strategies may be able to achieve.
Sensitivity analyses of species productivity and log price indicated a
high level of robustness in the results. Our study showed that reducing
forest health risks may be economically viable.