Key points

1. 1. Despite the popular image of ferns as decorative, innocuous plants, certain fern species can become substantial problems where human activities disturb the natural equilibrium. Making the distinction between native and alien species helps us to understand how some ferns become problematic in the first place and how such problems can be managed.

2. 2. About 60 species of ferns create problems for ecology and conservation in terrestrial and aquatic environments. Some of these ferns have significant negative impacts on human and animal health, food production and management of both land and water.

3. 3. Where legislative or other preemptive controls fail, problem ferns need to be managed by timely and effective combinations of physical, chemical and biological methods. Researchers continue to improve methods of managing problem fern species in order to enhance efficacy and to minimize damage to nontarget vegetation and the local environment.

4. 4. The full human, economic and environmental costs of problem ferns have not been investigated on a global basis. Continued international development of effective legislation and chemical and biological management of problem ferns will be required in order to contain their further spread which, in some cases, may be extensive and catastrophic.

Introduction

At least 60 fern species (see Table 8.1) have the proven or potential ability to occupy areas where they may create a variety of problems. The terrestrial ferns in this group can disrupt local ecosystems, conservation efforts, wildlife management and the productivity of land (including grazing lands, certain crops and forestry).