Farmers and honey producers often use specialist pollination services to truck honeybee hives around the country, augmenting the background natural pollination activities of bees and other pollinators. This gives the bees optimum access to floral resources for timely pollination, nectar collection and hive health, especially in spring when nectar and pollen are less widely available. The bees literally get a free ride, the flowering plants get to bear fruit and seed, the honey industry gets its 30%, and New Zealand’s primary sector thrives.
But where are the best floral resources, and when do they appear? What types of land and vegetation cover are best for bees? How many hives can a particular location support? And where should bees spend the winter, to help ensure hive health?
In a world-first, ecologist Dr James McCarthy and colleagues at the BSI have used powerful digital land cover mapping tools and vegetation survey data to create month-by-month maps of floral and pollen resources at a national scale.
The researchers used two land mapping tools – the national Land Cover Database (LCDB) and the Land Environments of New Zealand (LENZ) environmental classification – to produce month-by-month maps of potential nectar production, including beech-forest honeydew secreted by scale insects, and potential pollen production (kilograms per hectare) for the whole of New Zealand. Importantly, the map data were augmented with real data from over 7,300 vegetation plots from the New Zealand Vegetation Survey Databank, each of which measured all vascular plant species in a 400m2 area. This approach enabled much more precise floral and pollen resource estimates to be made than in previous studies. It also allowed estimates to be made of historical pre-European pollen and nectar resources, compared with present-day resources.
The maps show that some of the highest pollen and nectar-producing resources are found in indigenous forest vegetation, whereas landscapes historically cleared of forest for farming are much less productive of pollen or nectar. Public conservation land produces over half of the national floral resource, and Māori land contributes more floral resource per hectare than non-Māori land, largely because much has regenerating mānuka and kānuka. South Island beech forests are the most productive of sugars, whereas North Island and west-coast South Island forests produce the most pollen. Kāmahi (Pterophylla racemosa) produces the most nectar of any plant species in New Zealand, followed by tawa (Beilschmiedia tawa) and mountain horopito (Pseudowintera colorata). Weeping matipo (Myrsine divaricata) is the highest ranked winter flowering species. Overall, plants in the Cunoniaceae family and the Myrtaceae family are the most productive for pollen and nectar.
The maps are a useful tool to help ensure optimum foraging for bees across the country, especially in the spring – during which time native forest vegetation produces the most nectar and pollen. The estimates of floral production at a given location and time will help to ensure that areas are not overstocked with hives, and that hive concessions are managed appropriately especially on or adjacent to conservation land, particularly during the leaner months for pollen and nectar, and to ensure that native (non-honeybee) pollinators get their fair share.
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