Ecology, history, threats, and management of gumland ecosystems in Aotearoa | New Zealand

Gumlands are a critically endangered ecosystem, restricted to Auckland and Te Tai Tokerau (Northland) in Aotearoa | New Zealand. Gumlands usually form in areas once dominated by kauri, where slow decomposition produces poorly drained, infertile soils with a siliceous hardpan. These harsh edaphic conditions result in heathlands dominated by mānuka (Leptospermum scoparium agg.), tangle fern (Gleichenia dicarpa), and sedges (Machaerina teretifolia and M. brevifolia). Before human arrival, gumlands were likely to have been small and transient components of the landscape; however, more frequent and widespread fire following Polynesian and European arrival increased their extent. Gumlands now face a suite of threats, including changes to climate, fire regime, and land use, and increased weed invasion. Fire is a critical driver of gumland formation and persistence. However, alterations to the fire regime (intensity and frequency) facilitate invasion by fire-loving (pyrophilic) weeds, potentially resulting in a fire-begets-fire feedback loop that climate change will likely exacerbate. Despite the many and varied ecological and social values that gumlands hold, they remain poorly understood and, thus, there is a limited evidence base to inform management of contemporary threats. Importantly, gumlands are a product of coupled social and ecological processes, so future research must explore social-ecological feedbacks to identify pathways for increasing their resilience. Gumlands share threats (climate shifts, plant invasions, fire) with many other Aotearoa | New Zealand ecosystems; therefore, they may serve as a valuable model system for identifying more widely applicable approaches to reduce the impacts of such threats.