Future Events

Losing our edges: adjacent land-use intensification facilitates plant invasions into indigenous shrubland fragments

Speaker: Gretchen Brownstein.

Native shrublands were once common across the Canterbury Plains, but over time, conversion of land to other uses including irrigated pasture have contributed to their gradual decline. In this talk I will be discussing a study we recently published which found that spillover of nutrients and water from adjacent intensive agriculture is facilitating invasions by exotic plants into reserves set up to protect the last remnants of these native shrublands. We show that nitrogen enrichment, likely from irrigated animal effluent, is detectable 10 m inside reserve boundary fences. And we observed increases in exotic herbs and grasses, along with declines in native species, up to 30–40 m in from irrigated boundaries. These distances are significant as some of these reserves are only 100 m across, meaning that more than 60% of these reserves can be affected.

The ongoing effects of more intensive land use adjacent to the reserves could be managed with better rules around buffers. However, our study highlights the larger problem of establishing representative reserves that are too small. To maintain viable indigenous populations in other landscapes will require protection of blocks in the 100s of ha to avoid past mistakes in reserve design made on the Canterbury Plains.

Andersons Lagoon

Wrap up for an easy winter walk to Andersons Lagoon. This little known gem close to Palmerston (last BSO trip in November 2019) is accessed via a planted area along a grass pathway which opens onto a small but interesting saltmarsh and marginal plant communities at the closed mouth of Stony Creek. Contact Maia Mistral-Armour 027 2388498

Cyanobacteria

Speaker: Nicole Heaton. Cyanobacterial blooms pose a significant threat to freshwater ecosystems globally, fuelled by eutrophication and warming temperatures. More recent studies have shown that the associated heterotrophic bacteria community may have an influential role in cyanobacterial bloom dynamics. Are these interactions affecting blooms in the Ōtākou region?

Flowers of Annapurna

Speaker: Mike Small. The Annapurna Circuit is one of the great hikes of the world. More than 150 kms of trails pass from an altitude of 80m with subtropical rainforest to as high as 5500m high-alpine/ subarctic areas near the world's highest mountain pass at Thorung La. Culturally diverse, it is also a biodiversity hotspot as a result of the intersection of several floristic regions and extremes of precipitation and altitude. Floral diversity also results from numerous geological uplifts that formed the Himalaya and the monsoon after India collided with Asia 50 million years ago. This talk follows the trail and the flowers during the monsoon flowering season of 2024.