Trees, People, and the Environment: using a tree planting site to engage a local community with climate change and biodiversity issues

Planting native trees is an important response to climate change and biodiversity loss in Aotearoa New Zealand, but it can be difficult to relate trees in the ground to measurable benefits. This study uses a community tree planting site next to the Ōtaki River to measure site-specific benefits. These are then used to inform science communication that is directly relevant to the local community. The study has a transdisciplinary approach, with expert input from a variety of fields, including biological science, community engagement, science communication, mātauranga Māori, and design. A participatory method was used, with the author volunteering within the community tree planting group Friends of the Ōtaki River, and meeting with local Māori in Ōtaki as part of community engagement.

In the scientific component of the study, carbon in trees was estimated using allometric equations, and carbon in soil by testing samples in a lab. Biodiversity values were measured by conducting five-minute bird counts, and using pitfall traps to count invertebrates at the site. The trees have been planted over a 20-year period, and changing biological values were measured between planting sites of different ages. Rather than showing clear linear trends, the research showed a complex ecosystem with many elements influencing carbon sequestration and biodiversity. Ecosystem processes such as canopy closure and habitat fragmentation were more influential in bird and invertebrate assemblages than simple tree size. The development of the ecosystem is in turn influenced by biodiversity, such as through seed dispersal.

In order to communicate the complexity of carbon absorption and biodiversity at the site, key messages were developed about the range of ecosystem services provided by trees, ecosystem processes in different stages of growth, the long timeframes required for carbon to accumulate and associated importance of large trees, and that native biodiversity is related to the amount of tree cover. Communication outputs were developed to share these messages in a way that related directly to the community in Ōtaki. Carbon absorption over time was compared to carbon dioxide emissions generated by everyday activities within Ōtaki, and biodiversity values were related to the visible development of the ecosystem as the plantings grow. Signage is proposed for installation along the Ōtaki River walkway to communicate key messages to the local community.