Mānuka Forest Biodiversity Boost: New Research Reveals Benefits of Large-Scale Planting

New research published in the New Zealand Journal of Ecology highlights a promising pathway for restoring biodiversity on marginal farmland through large-scale Mānuka forest planting. Conducted on a central North Island property, the study demonstrates how converting low-productivity pasture to Mānuka (Leptospermum scoparium) shrublands not only supports lucrative honey production but also fosters rapid ecological recovery. This case study offers evidence-based insights into balancing agricultural economics with environmental stewardship in Aotearoa New Zealand. 53 51

🌿 Understanding Mānuka and Its Role in New Zealand's Landscape

Mānuka, a resilient native shrub endemic to New Zealand, thrives in poor soils and harsh conditions, making it ideal for revitalizing unproductive hill-country pastures. Its flowers produce highly prized monofloral Mānuka honey, renowned for unique antibacterial properties due to high levels of methylglyoxal (MGO). The industry has grown exponentially, with New Zealand's beekeeping sector valued at around NZ$448 million in 2026, driven largely by Mānuka exports. 42

Historically, Mānuka formed vast shrublands before European settlement and intensive farming converted much of it to pasture. Today, landowners facing declining sheep and beef profitability—exacerbated by droughts and market fluctuations—are turning to Mānuka plantations. Companies like Comvita have planted over 6 million trees since 2017, creating more than 6,300 hectares of forest and sequestering 130,000 tonnes of CO₂ equivalent. These efforts promise annual returns of NZ$100-150 million from plantation honey by the late 2020s.

The Groundbreaking Case Study: Methods and Sites

Led by researchers including Georgia N. Woodall and David E. Pattemore from the University of Auckland and Plant & Food Research, the study employed a space-for-time substitution approach on a single property. Four sites represented progression stages: 34 ha pasture, 36 ha three-year-old planted Mānuka, 23 ha five-year-old planted Mānuka, and 57 ha naturally regenerated Mānuka forest over 30 years old. Surveys included terrestrial invertebrates via window traps, bat and bird acoustic monitoring, and independent stream macroinvertebrate assessments using the Macroinvertebrate Community Index (MCI).

This methodology allowed comparison of biodiversity trajectories without long-term waiting, though the authors note the need for replication across sites to generalize findings. 53

Key Biodiversity Findings: Insects, Birds, and Bats

Terrestrial invertebrate abundance and diversity dipped in three-year-old plantings compared to pasture, likely due to canopy closure reducing open-ground species. However, by five years, both metrics surpassed pasture levels and mirrored the mature forest's community composition. Bird surveys echoed this: younger plantings initially lagged, but five-year-old sites hosted richer assemblages.

Particularly striking was the detection of critically endangered long-tailed bat (Chalinolobus tuberculatus) calls, more frequent in five-year-old and mature Mānuka than in pasture or young plantings. These bats, New Zealand's smallest and most threatened, rely on insect-rich forests for foraging. 52

• Invertebrate diversity rebounds rapidly post-year 3.
• Bird communities stabilize by year 5, supporting natives like fantails and grey warblers.
• Bat presence indicates high insect biomass, a key ecosystem health indicator.

Stream Health Improvements from Mānuka Catchments

Freshwater sites draining Mānuka or native forest showed superior health versus pasture-dominated streams. Higher MCI scores reflected cleaner water, reduced sedimentation, and robust macroinvertebrate communities—crucial for fish like native galaxiids. Mānuka's dense roots stabilize soils, mitigating erosion on steep hill country, a chronic issue in pastoral farming.

This aligns with prior research on Mānuka's erosion control efficacy, enhancing riparian buffers and nutrient filtration. 53

Photo by Sung Jin Cho on Unsplash

Economic Incentives Driving Large-Scale Planting

With sheep/beef farm profits volatile, Mānuka offers stable income from low-input land. Plantations yield 10-20 kg/ha of premium honey annually after year 3, with global Mānuka demand projected to push market value beyond US$1.2 billion by 2033. Government programs like the Primary Growth Partnership have funded high-performance varieties, optimizing growth and honey yield.

Comvita's model exemplifies integration: biodiversity monitoring embedded in commercial operations, proving dual economic-ecological viability.MPI's High Performance Mānuka Plantations

Challenges and Nuanced Perspectives on Honey Bee Impacts

While planting benefits shine, introduced honey bees pose risks. A December 2025 New Zealand Journal of Ecology paper found high hive densities in Mānuka shrublands alter invertebrate communities, potentially competing with natives. Balanced management—limiting hives during peak native pollination—is recommended.

Other hurdles include weed invasion in young plantings, pest threats like myrtle rust, and end-of-life wood utilization for bioenergy to avoid waste. 10

University of Auckland's Pivotal Role in Mānuka Research

Affiliates like Dr. David Pattemore, formerly at Plant & Food Research, underscore higher education's contribution. The University of Auckland's School of Biological Sciences provides expertise in pollination ecology, supporting industry-academia partnerships. Such collaborations train students in applied ecology, addressing NZ's biodiversity crisis amid 80% native bird decline since human arrival.

Prospective researchers can explore opportunities via AcademicJobs NZ listings.

Broader Environmental Co-Benefits: Carbon, Soil, and Water

Mānuka plantations sequester carbon effectively—up to 10-15 tCO₂/ha over 20 years—qualifying for NZ Emissions Trading Scheme credits. They improve soil fertility via nitrogen fixation and organic matter buildup, reversing pastoral degradation. Water quality gains from reduced runoff position Mānuka as a tool for freshwater restoration under Te Mana o te Wai policy.

Stakeholder Perspectives and Future Directions

Comvita's Dr. Jackie Evans notes: "Mānuka planting delivers measurable, rapid gains for native ecosystems." CEO Karl Gradon emphasizes scalability. Farmers report diversified income, but call for policy support like subsidies for biodiversity monitoring.

Future research priorities: multi-site replications, long-term monitoring, genetic selection for dual-purpose cultivars. Integration with agroforestry could amplify benefits. 51

Photo by Katie McBroom on Unsplash

Policy Implications for Sustainable Land Use in New Zealand

This study bolsters arguments for incentivizing native shrublands over exotic forestry or continued pastoralism. Aligning with He Waka Eke Noa and National Policy Statement for Indigenous Biodiversity, Mānuka offers a 'win-win' for climate, economy, and nature. Universities like Auckland advocate evidence-based guidelines to maximize outcomes.

Explore ecology careers shaping NZ's green future at research positions.