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Fenced Forests Flourish: A Pig-Free Future?
2 Oct
Summary
- Feral pigs significantly damage Hawaiian wet forests through feeding and trampling.
- Protected forest sites showed a six-fold increase in woody plants over 16 years.
- Nonnative plants like strawberry guava also increased significantly at protected sites.
Hawaiian wet forests, unique ecosystems that evolved without large mammals, are highly susceptible to damage from feral pigs. These invasive animals alter vegetation through feeding and trampling, potentially facilitating other species' spread. Research in Hawaiʻi Volcanoes National Park examined forest recovery by comparing fenced areas, excluding pigs, with unfenced sites over 16 years.
Sites protected from pigs demonstrated significant ecological regeneration. Over the study period, these areas saw a six-fold increase in woody plants rooted in mineral soil and a substantial rise in young tree fern density. In stark contrast, areas with pigs experienced a dramatic decline in herbaceous cover.
However, the absence of pigs did not solely benefit native species. Invasive plants, such as the strawberry guava, also saw a five-fold increase in density at the pig-free locations. Another study at Hakalau Forest National Wildlife Refuge, monitoring ungulate management from 1987 to 2004, noted an increase in native ferns and a decrease in exposed soil and bryophytes.
These findings suggest that reducing or removing non-native ungulates can aid native vegetation recovery. Yet, the degree of recovery varies by ecosystem. Experts emphasize that controlling invasive plants and reintroducing rare native species may be necessary alongside pig exclusion for comprehensive forest restoration.
