Forest ecological integrity in Tāmaki Makaurau 2009-2024. State of the environment reporting

Extract from the Executive summary:

This report assesses forest ecological integrity in Tāmaki Makaurau / Auckland, with a focus on forest extent and configuration using data from the Landcover database from 1996-2018 with a provisional update to 2023, and forest composition, structure and function using plant and bird data from Auckland Council's Terrestrial Biodiversity Monitoring Programme (TBMP) 2009 to 2024. Ecological integrity is defined as the extent to which an ecosystem is able to support and maintain its composition, structure and functions, in comparison to its natural or historical range of variation and in response to natural or anthropogenic change.

Forest extent

Indigenous forest and scrub account for 27% of land cover in Tāmaki Makaurau, up from 26% in 2018. Indigenous forest covers 16.8% (81,161 ha) and indigenous scrub/shrubland 11.3% (57,999 ha). Across the 27-year monitoring timeframe, the largest expansion in forested land cover was observed 2018-2023, with net gains of 1,021 hectares of indigenous forest and 4,534 hectares of indigenous scrub/shrubland. 

The primary driver of forest expansion is conversion from exotic grassland (1,839 ha for forest, 4,680 ha for scrub/shrubland), with additional gains from exotic forest (439 ha to forest, 697 ha to scrub/shrubland). Gains arise from active replanting associated with pastoral conversion to lifestyle blocks and greenfield developments, active replanting in regional parks, and natural regeneration on marginal farmland. Approximately 84% of gains occurred on private land, with the 10 largest patches accounting for 7% of total gain and often associated with rural subdivisions and lifestyle development.

A mixture of Auckland Unitary Plan policies are driving these changes, including rural subdivision rules (E39), vegetation management and biodiversity provisions (E15) particularly when developments impact existing ecological features or require ecological offsets, planting to protect water quality (E3), and Significant Ecological Areas overlay (D9). Public land gains were concentrated in regional and local parks, with Te Muri Regional Park recording the largest increase (approximately 75 ha).

Gains and losses are not equivalent for biodiversity. All indigenous forest ecosystems in Tāmaki Makaurau are classified as Threatened according to International Union for Conservation of Nature (IUCN) criteria. Forest losses result from direct conversions to urban expansion (187 ha) and infrastructure development, or from incremental infill that crosses classification thresholds. There will be considerable time-lag before new plantings can compensate for loss of biodiverse habitats when existing forest is removed. The ecological outcomes of large-scale planting programmes depend on the quality of initial planting and maintenance. Low-diversity plantings on private land may fall short of supporting diverse, self-sustaining indigenous ecosystems without careful planning of diverse species mixtures, and ongoing monitoring. Despite recent gains, Tāmaki Makaurau remains well below the national average of 33% indigenous forest cover. ...

Auckland Council technical report, TR2025/22

September 2025

See also

Te oranga o te taiao o Tāmaki Makaurau. The health of Tāmaki Makaurau / Auckland’s natural environment in 2025. A synthesis of Auckland Council’s state of the environment reporting