By Guest Author 17/05/2021


Steve Trewick

She’s a scarlet, long-legged stunner with dainty white feet, and the male of the species is almost as impressive. Yet this stunning creature has rarely been seen and was only this year formally recognised.

Hemiandrus jacinda is a ground wētā named this year for New Zealand’s Prime Minister Jacinda Ardern

Most of us are aware of distinctive New Zealand species. Kiwi and kākāpō for example are unusual birds specific to New Zealand and frequently in the news, but our bird diversity is relatively small and well-recognised. There are today a little over 200 species of native birds in New Zealand, but there are an estimated 20,000, yes twenty thousand, native insect species, of which more than 80% are endemic to this land (found nowhere else on the planet). Given the number it is not surprising that about half of those insects (moths, beetles, flies, bees, wētā etc) have not yet been formally recognised. And then there are the millipedes, spiders, mites, land-hoppers etc… About 22,000 New Zealand arthropods (invertebrates with an exoskeleton and jointed legs) have been described but we have a similar number to get to grips with. Oh, let’s not forget the flat-worms and worms, the slugs and the snails.

To put that in some sort of context, consider the United Kingdom is only slightly smaller than New Zealand and home to abut 24,000 species of insects. One of those insect species is endemic to the UK. That means the level of endemicity among UK insects is less than 0.005%. More precisely, that one endemic species is a small moth called Eudarcia richardsoni; one species out of an impressive 2,500 Lepidoptera (moths and butterflies) known to occur in the UK (endemicity of ~0.04%). The New Zealand Lepidoptera fauna is a bit smaller in terms of total numbers of species; it includes about 1,800 species. Of these, approximately 1,600 are found nowhere else in the world. In other words about 90% of New Zealand butterflies and moths are endemic and if lost from New Zealand would be lost from the world. And there’s the rub.

The dearth of endemic species in the United Kingdom is not for want of trying; the entomology collections of the Natural History Museum in London, for example, number more than 34 million insect and spider specimens, amassed over 300 years. No, here lack of endemicity is not a lack of discovery. It is because the UK biota is shared with western Europe; the plants, animals, fungi, microbes and humans (Cheddar man) arrived in Britain as the last glacial maximum (LGM) receded about 18,000 years ago. Before that an icy climate and polar ice sheet excluded life from the region. The same global climatic cycling affected the Southern Hemisphere including New Zealand but long distance from the Antarctic ice sheet and temperature buffering by the ocean allowed an existing biota to survive through the Pleistocene glacial phases. The net result is a biota in New Zealand evolved over millions of years rather than one dominated by arrival over fewer than 20,000 years as in the UK.

Decline over 40 years

Despite the lack of insect endemicity in the UK, insect biodiversity is ecologically and culturally valued. Entomologists across Europe are justifiably concerned about recent declines in species richness and waning populations of many formerly common insects. Declines are now documented across the landscape including the reserves established to protect native plants and animals. As insects and other invertebrates mediate many aspects of plant biology including pollination and are essential prey for many vertebrates, their loss is predicted to destabilise fundamental ecosystem functions.

The challenge for the UK and Europe is to identify changes in species richness and population size among an already well-studied biota and respond to it. For New Zealand the problem is more complex as it involves discovering the diversity at the same time as documenting changes in abundance and finding solutions.

Continued decline of NZ native habitats

The reasons for the declining abundance and diversity of insects and other organisms are well recognised. They relate primarily to habitat loss. Since the 1950’s the UK has destroyed almost all of its ancient, native, flower-rich meadows (97%) and half of its ancient woodlands, with similar trends across Europe. The remaining native, complex ecosystems with rich biodiversity are fragmented and less resilient.  In New Zealand the dominant vegetation when humans arrived was forest; native herb-rich grasslands were a limited feature of our landscape outside the alpine zone. The process of landscape change was extremely rapid and extensive as European colonists developed a pastoral economy using a small number of European grass and herb species. Two thirds of the ancient forests, the majority in lowland areas favoured for farming, have been erased. These forest were not just havens of biodiversity but among the most important carbon reserves on the planet. Moves are being made to establish a more inclusive and moderated approach to the landscape, but this will not return substantial, biodiverse native forests in a hurry. Meanwhile pastoral intensification continues.

Formally describing the dwindling populations of endemic insects and other small animals is already beyond our current capacity. There are too few scientists with the necessary skills and time. Understanding the biology of these animals and their interactions with each other and their environment is even more remote. Looking away is not an option.

So, welcome jacinda. See you around, I hope.