Ecological Monitoring: A Detailed Study
Introduction
Nestled on the northern side of Dansey Road, approximately 13 km northeast of Rotorua, lies the Dansey Road Scenic Reserve. This 468-hectare expanse, intersected by the now scenic Rotorua railway line, is dominated by primary rimu and tawa forest. Despite the pervasive presence of small animal pests like possums, rodents, and predators, the reserve remains free from large herbivores such as deer, feral goats, pigs, and wallabies. Consequently, much of the forest's understorey is remarkably intact and rich in palatable plant species, including pikopiko, toropapa, hangehange, and large-leaved coprosma shrubs.
Background and Purpose
Since its inception, the Canopy Conservation Trust (CCT) has undertaken extensive multi-species pest control within the reserve. The sustained pest management led to noticeable impacts on the local flora and fauna. Over the years, the pest control program's scale and intensity have increased, now covering 187 hectares south of the railway line. This intensive effort has led to perceptible improvements in forest health, such as the recovery of possum-palatable species and the return of native birds like the North Island Robin and Tomtit.
Ecological Outcome Monitoring
CCT has employed various methods to monitor pest populations, including the use of chew cards and tracking tunnels. However, measuring pest abundance alone does not provide insights into the impacts on native species populations. Therefore, the project aims to establish suitable, achievable, and meaningful measurements of the health of indicator native species populations within the reserve, resulting from the pest control efforts.
Monitoring Indicators
Indicator species are a small subset of species that reflect broader ecological health trends. Ideal indicators are widespread, have well-understood biology, and are relatively abundant. They should also be easy to locate and monitor in the field, providing clearly measurable data.
Possum Control Outcomes
Possum Diet Patterns
Possums are known to affect various native species by their browsing habits. Their diet includes a wide range of native plants, leading to significant ecological impacts. Monitoring their diet patterns helps in understanding the extent of their impact on the ecosystem.
Key Indicators of Success
Kohurangi (Kirk’s Tree Daisy): This species serves as an important indicator of possum control success. Monitoring its health and abundance provides valuable insights into the effectiveness of pest management strategies.
Tawari: Another critical indicator, tawari, is highly susceptible to possum browsing. Its recovery signals successful pest control efforts.
Palatable Shrubs and Small Trees: The presence and condition of species such as kotukutuku, whauwhaupaku, and raukawa are monitored to assess the impact of possum control on the forest understorey.
Mistletoes: Known for their sensitivity to possum predation, the recovery of mistletoe populations is a positive indicator of successful pest control.
Kohurangi - Kirk’s Tree Daisy (Brachyoglottis kirkii var. kirkii)
Rat Control Outcomes
Kokako
One of the primary goals of rat control is to provide safe breeding conditions for native birds like the kokako. Monitoring the success of rat control efforts involves several key indicators:
Five-Minute Bird Counts: This method provides data on bird population trends over time, helping to gauge the impact of rat control measures.
Toutouwai and Miromiro: These bird species are particularly vulnerable to rat predation. Monitoring their populations helps in assessing the effectiveness of rat control.
Kereru: This native pigeon’s breeding success is closely tied to rat populations. Regular monitoring helps in understanding the broader ecological impacts of rat control.
Additional Monitoring Methods
Weta Boxes: These provide a habitat for weta, a native insect species. Monitoring their populations helps in understanding the impact of pest control on invertebrate species.
Lizards: Though labor-intensive, monitoring lizard populations provides critical data on the impacts of pest control on these vulnerable species.
Forest Gecko (Mokopirirakau granulatus)
Detailed Analysis of Possum and Rat Control Efforts
Possum Control
Possums (Trichosurus vulpecula) have been a significant threat to New Zealand's native ecosystems due to their broad diet, which includes many native plant and animal species. Effective control of possums has shown positive outcomes for various flora and fauna in the Dansey Road Scenic Reserve.
Vegetation Impact: Possum control efforts have resulted in noticeable regeneration of several native plant species. For instance, monitoring has shown a significant increase in the abundance and health of kohurangi (Brachyglottis kirkii) and tawari (Ixerba brexioides). The resurgence of these species is a clear indicator of reduced browsing pressure.
Biodiversity Recovery: The decrease in possum numbers has led to the recovery of palatable shrubs and small trees such as kotukutuku (Fuchsia excorticata), whauwhaupaku (Pseudopanax arboreus), and raukawa (Raukaua edgerleyi). The resurgence of these species is crucial for maintaining a balanced and diverse understorey.
Rat Control
Rats (Rattus spp.) pose a significant threat to native bird populations due to their predation on eggs, chicks, and even adult birds. Effective rat control is essential for the survival and reproduction of many native bird species in the reserve.
Bird Population Dynamics: Regular five-minute bird counts have indicated an upward trend in native bird populations, particularly species that are vulnerable to rat predation. For instance, the North Island robin (Petroica longipes) and tomtit (Petroica macrocephala) populations have shown considerable growth.
Kereru Breeding Success: The breeding success of the kereru (Hemiphaga novaeseelandiae) has improved markedly with effective rat control. The kereru is a critical species for forest regeneration as it disperses large seeds. Monitoring data indicates an increase in kereru fledging rates, which correlates with reduced rat populations.
Weta and Lizard Monitoring
Monitoring the populations of weta and lizards provides insights into the broader ecological impacts of pest control.
Weta Population Trends: Weta (Anostostomatidae) are sensitive to changes in predator populations. The use of weta boxes has shown an increase in weta numbers, indicating successful control of their predators. Data collected from these boxes helps in understanding the long-term trends in weta populations.
Lizard Observations: Though monitoring lizards is labour-intensive, it is essential for understanding the full ecological impact of pest control. Regular surveys have shown stable or increasing populations of several native lizard species, suggesting a positive outcome from pest management efforts.
GIS and iNaturalist Integration
To enhance data management and accessibility, TrapNZ is used to collect, analyse and share data on both pest eradication and population levels of pest-sensitive species. This improves the overall monitoring of the program and provides a historical database to analyse and work forward from.
Collaboration and Research
Collaborating with academic institutions such as Waikato University can provide valuable research opportunities and additional monitoring measures. Engaging students in monitoring efforts not only enhances data collection but also promotes conservation awareness and education.
Recommendations
Clear Goals and Objectives: Documenting specific goals and objectives for pest control efforts is crucial for evaluating success and guiding future actions.
Control Areas: Establishing non-treatment areas as controls helps in comparing treated and untreated zones, providing clearer insights into the effectiveness of pest management strategies.
Indicator Species Monitoring: Focus on monitoring key indicator species such as weta, kereru, and kohurangi to gauge the impact of pest control efforts.
Data Management: Implementing a robust data management system, through TrapNZ, GIS or iNaturalist, streamlines data collection and analysis.
Research Collaboration: Partnering with academic institutions for research can enhance monitoring efforts and provide valuable data for adaptive management.
Conclusion
The comprehensive ecological monitoring at Dansey Road Scenic Reserve underscores the importance of sustained pest control efforts. By focusing on key indicator species and employing robust monitoring methods, CCT can continue to enhance the health and biodiversity of this unique forest ecosystem. Through ongoing research and adaptive management, the reserve can serve as a model for effective conservation practices in similar ecological settings.
Statistical Summary
Possum Control Area: 187 hectares
Primary Vegetation: Rimu and tawa forest
Key Indicator Species: Kohurangi, tawari, kotukutuku, whauwhaupaku, raukawa, mistletoes, kokako, toutouwai, miromiro, kereru, weta, lizards
Bird Population Trends: Significant increase in North Island robin and tomtit populations
Kereru Fledging Rates: Marked improvement with effective rat control
Weta Box Data: Increasing trends in weta populations
Lizard Survey Results: Stable or increasing populations of native lizard species
Final Thoughts
The success of the ecological monitoring and pest control efforts at Dansey Road Scenic Reserve highlights the importance of targeted conservation strategies. By continuously adapting and improving these efforts, we can ensure the long-term health and resilience of this precious ecosystem, benefiting both its flora and fauna for generations to come.
Appendices
Appendix A: Monitoring Methods
Five-Minute Bird Counts: Conducted biannually, recording all bird species seen and heard within a five-minute period at designated points.
Weta Box Monitoring: Boxes checked quarterly, counting and recording weta present.
Lizard Surveys: Conducted twice a year, using pitfall traps and visual encounter surveys.
References
Rotorua Canopy Tours. (2023). Ecological Monitoring Report.
New Zealand Department of Conservation. (2023). Pest Control Guidelines.
Waikato University. (2023). Research Collaboration Agreement.
