Case Study Overview

This case study illustrates the diverse functionalities of the FCP through the analysis of Catchment Management Units (CMUs) within the larger Wairoa Catchment in Northern Hawkes Bay. It explores questions that have been raised during our stakeholder engagement discussions with Iwi, Regional Councils, and Forest Industry Representatives across Te Tauihu (Top of the South Island), Tairawhiti (Gisborne) and Te Matau-a-Māui (Hawkes Bay). The study demonstrates how the FCP tool can improve understanding and decision-making for sustainable environmental management in the Wairoa Catchment. Additionally, it explores how these stakeholders can ensure long-term stewardship by identifying and planning to address potential risks associated with plantation forest harvesting upstream.

Wairoa Catchment

Hawke’s Bay catchments have been grouped into seven ‘catchment zones’. The Wairoa and Northern Catchments is one such zone (See image below).

This large zone includes the main Wairoa catchment and smaller coastal catchments of Whakaki, Nuhaka and Mahia. The Wairoa catchment covers 3,674 km2 and drains the eastern flanks of the Te Urewera and the Huiarau Range. Rivers and lakes are integral to the catchment’s character and wellbeing: these comprise Lake Waikaremoana and Lake Waikereiti, and the Wairoa, Waiau, Waikaretaheke, Mangaaruhe, Ruakituri, Hangaroa and Mangapoike Rivers. The Wairoa River is significant to the iwi and hapū of Te Rohe o Te Wairoa, ecologically as well as for recreation and mahinga kai. Lakes, river systems and coastal lagoons/wetlands are ecologically rich, supporting native fish, including critically threatened longfin eel and koaro. There are large populations of brown and rainbow trout in many rivers. Water quality is generally good, but suspended sediment and poor visual clarity are issues caused by a combination of erodible soils, high rainfall and land use practices. Soft sedimentary (“soft-rock) hill country is dominant with hard greywacke and argillite forming higher hill country in the west. Soft-rock hill country landscapes are susceptible to erosion, and intense rainfall and tectonic activity trigger frequent landslide erosion events. The alluvial sediments of the lower Wairoa valley and coastal plain are naturally fertile, but with areas of poor drainage. Indigenous forest dominates in the greywacke ranges of Te Urewera in the west, but elsewhere hill country pasture and commercial forestry predominate. There has been transition from pastoral farming to plantation forestry in recent years, particularly on economically marginal land. Intensive cropping and horticulture occur on limited areas of fertile lowlands. The Wairoa catchment is sparsely populated with small communities. Wairoa is the only main service town, with SH2 links to Napier and Gisborne, a small airport and rail link (freight only). The small rural centre of Frasertown includes basic services. Many rural roads are unsealed. The zone has a declining population with significant outmigration of younger people. There is a higher proportion of lower incomes than the rest of region. The local economy is dominated by primary production and processing, with heavy reliance on two main processing works for employment. Forestry is of growing importance. Coastal/ecotourism and recreation are the other economic drivers.

(Sources: Reed, Chris and Ide, Gavin (2012) Hawke's Bay Catchment Zone Profiles July 2012. Report SD 12/08. HBRC Plan Number 4337. Hawke’s Bay Regional council, Napier. AND Smith HG, Vale S, Neverman A, Robson-Williams M, Harris L. 2022. Climate change impacts on suspended sediment loads in the Wairoa catchment, Hawke’s Bay. Manaaki Whenua - Landcare Research Contract Report LC4121 prepared for the Our Land & Water National Science Challenge.)

Tangata Whenua

What forestry activity is happening upstream of Iwi and Hapu land that may impact intergenerational decisions?

The FCP is designed to enable and empower Iwi and Hapu to embody the Tikanga of rangatiratanga (leading the industry in this space), kaitiakitanga (positive change to sustaining natural resources) and kotahitanga (unity among the industry for a collective purpose). Iwi and Hapu can use the FCP to understand where forestry activity is anticipated to be happening upstream of their whenua (“land”) which can help with intergenerational planning and thinking about impacts abreast of severe storm events.

The project acknowledged the importance of Iwi perspectives and sought to provide a medium to allow their voices to be heard and respected in environmental management efforts. The tool can be used to see where Marae and maori land intersects with catchment management units and visualise forestry activity over time upstream.

For instance, the Te Reinga Marae, located in the Te Reinga settlement of Ruakituri, is the central, cultural hub for the Ngāti Hinehika hapū. It holds significant historical and cultural value, serving as a venue for community events, ceremonies, and meetings. Situated within Catchment Management Unit (CMU) 2968, selecting this CMU in the FCP reveals forest stands and key infrastructure elements like bridges, roads, railways, streams, and buildings. Playing the timeslider animation can help Iwi and Hapu get an idea of when blocks are likely to be harvested and how long they will likely be in a window of vulnerability for. Turning on the Marae and Māori land blocks can give Iwi and Hapu insight into what affects them over time.

Regional Councils

Which areas of forestry are expected to be in the window of vulnerability over the coming years?

Councils manage land at landscape scales and can use the FCP to visualise where large tracts of forests are likely to be within the window of vulnerability (WoV) by using the time slider to slide back and forward through time.

The time slider feature in the FCP provides a visual timeline of likely future harvesting events based on the typical harvest age of 28 years for forestry blocks. This tool is particularly beneficial for regional council planners and land use officers as it offers clear insights into predicted concentrated clearfell harvesting. By identifying areas undergoing significant harvesting, planners can foresee periods when large tracts of land will be in the WoV for five years post-harvest. This understanding is essential for planning mitigation strategies to prevent erosion, maintain water quality, and ensure landscape stability during these critical periods. The age class data provided by the FCP is a crucial tool for informed planning and policy-making. Understanding the age distribution of forest stands allows planners to anticipate future harvesting activities and their impacts, enabling the development of policies that promote sustainable land use and mitigate environmental hazards.

For instance, the FCP's time slider reveals that a significant forestry block along Bushy Knoll Road in the Gisborne region, within the Wairoa Catchment, is forecast to reach maturity in 2030. If clear-felled, this vast area will become highly vulnerable. This is particularly important as a bridge along this road was recently replaced after being destroyed during Cyclone Gabrielle, which highlights the potential risks in future years. Council staff need to manage these risks in six years, making this an ideal candidate for staged harvesting over several years to spread the risk. By integrating age class insights into their planning processes, council planners can better coordinate land use activities, prioritise interventions, and foster a resilient and sustainable approach to managing the catchment area.

Forestry Industry

What parts of the forests we manage require the greatest care and attention when planning and harvesting?

The landslide susceptibility and Melton ratio modeling within the FCP can help forestry management companies quickly identify areas requiring the greatest care and attention during planning and harvesting.

The FCP provides an additional tool for forest managers to enhance environmental risk assessments through landslide susceptibility and Melton ratio modeling. When a forest stand is selected, the FCP calculates these attributes to offer a detailed understanding of potential landslides and erosion risks. The landslide susceptibility calculation evaluates the likelihood of landslides based on environmental and topographical factors, identifying high-risk hillslope units within forest stands. The Melton ratio, relating catchment area to relief, assesses erosion potential and landscape stability. Each forest stand may have multiple ratings, reflecting diverse conditions and varying degrees of risk. These functions enable managers to make informed decisions regarding land use and management practices, ensuring proactive measures to mitigate potential hazards. This data facilitates efficient planning and scheduling of harvesting activities, allowing managers to minimise environmental impacts and ensure sustainable practices.

For instance, the selected forest stand in Te Koparetangihanga shows clearly defined areas of heightened landslide susceptibility and higher Melton ratio ratings. This visual representation provides forest managers with risk information for specific sections of their blocks. By identifying these high-risk areas, managers can implement thorough erosion control measures and plan harvest activities more carefully. This targeted approach helps mitigate potential hazards, ensuring sustainable and responsible forest management. By using the FCP to assess risks and strategise accordingly, managers can optimise operations, avoid high-risk areas, and protect critical infrastructure, promoting long-term sustainability and resilience within forest stands.

Conclusion

For the first time ever, councils, Iwi, Hapu, and forestry management companies can have meaningful conversations about land management in relation to forestry harvesting cycles across multiple regions and catchments, spanning through time. Historically forestry and land vulnerability data was fragmented, inconsistent and typically inaccessible. Now, with consistently visualised and factually based datasets, stakeholders can engage in well-informed, transparent discussions. This collaborative approach ensures that environmental and cultural values are upheld, promoting sustainable and resilient land management practices for future generations.