The Impact of Feral Pigs on Rainforest Dynamics in North-Eastern Australia

Feral pigs threaten biodiversity worldwide by altering ecosystem structure and function. The most noticeable effect of pigs on ecosystems is disturbed soil caused by their rooting foraging behaviour, which can impact upon invertebrate populations, nutrient cycles, and plant regeneration. In this study, we assessed the impact of feral pigs on rainforest dynamics in north-eastern Australia by comparing plots where fencing had been used to exclude pigs for 2 and 14 years with unfenced plots at continual risk to pig damage in both the wet and dry seasons. Rainforest dynamics were quantified using a range of earthworm, soil, litter, and plant characteristics, and we used mixed linear models to explain the response of these variables to both plot type and season. Our results show that feral pigs do not have a strong impact on rainforest dynamics. The only significant result was greater litter moisture in the fenced compared to unfenced long-term plots. In contrast, the majority of response variables exhibited significant seasonal differences. For the plot type and season interaction effect, the only significant result was litter biomass in the long-term plots. There was no significant difference between means for the fenced and unfenced plots within the wet and dry seasons; however, litter biomass was greater in the unfenced plots during the wet season and, conversely, greater in the fenced plots during the dry season. Overall, our results show that season has a greater impact on rainforest dynamics than feral pigs