In module II, we examine two indicators of sustainable forest management: the maintenance of biodiversity and maintenance of forest health. These two aspects are related, since the pathogens that occur within a forest are a part of its biodiversity, and physical (abiotic) disturbances can play an important role in maintaining the diversity of species present in a forest. As we go through this module, you will gain an understanding of how this works.
Maintaining forest biodiversity is a critical aspect of forest management. It is particularly important when considering the management of natural and semi-natural forests, but increasingly there have been concerns about making plantations more “biodiversity-friendly”. There are a variety of different steps that a manager can make to achieve this goal, and many of them are context specific. For example, the steps taken to maintain biodiversity in a temperate rainforest in western Canada, dominated by Sitka spruce (Picea sitchensis), western hemlock (Tsuga heterophylla) and western redcedar (Thuja plicata), will be very differed from those taken by the manager of a commercial plantation of Sitka spruce in western Scotland. The differences between the management of a temperate rainforest and a tropical rainforest may actually be less apparent and, as you will see during this module, many of the principles involved are transferrable.
Biodiversity encompasses not only species diversity but also ecosystem diversity and genetic diversity, as well as the processes maintaining these different types of diversity. One of the most important processes is natural disturbance. Natural disturbances can occur at a range of scales, affecting individuals, single species, patches of forest or even an entire ecosystem. In many situations forest management seeks to minimize natural disturbances, replacing them with anthropogenic disturbances, principally forest harvesting. This is not always wise: years of fire suppression in many forested areas have actually resulted in a decline in forest health which is now having to be rectified through very expensive remediation measures. In British Columbia, stand treatments to reduce fire hazard cost on average $10,000 a hectare. Given that there are well over a million hectares needing treatment, the cost is phenomenal. Similar work is required throughout western North America, from California to Alaska.
Foresters in some parts of the world, especially in Europe, have also been concerned with forest sanitation, keeping the forest as free as possible from diseases and insects. This is also a problem, as a significant proportion of a forest’s biodiversity is dependent on dead wood, whether standing or lying on the ground. The removal of dead and dying trees reduces the habitat for many of these specialist species.
In this module we will also examine the role that climate change plays. This is complex, and introduces an entirely new dimension to the forest biodiversity and forest health debate. Essentially, why these criteria deal with maintaining particular values, climate change means that these values are going to be even more dynamic than they already are. For example, a warmer and/or drier climate will result in changes in the composition of the species within a forest, and may alter the patterns of natural disturbance. This presents significant challenges for managers, which are examined in this module.