Recent work on Ohinau Island, Coromandel reinforced for me how fine the boundary is between the sciences. We were working on the biology of shearwaters nesting at an important historical site for Ngati Hei, an iwi from the eastern Coromandel.

The island has been inhabited in the past, and was an important food gathering site for Ngati Hei. During or work at night on shearwaters, our head-torches illuminated the many small shards of obsidian in the upper surface of the soil.

We found several small obsidian pieces, mainly around the areas we were working extensively in the south of the island near shearwater nest sites. Obsidian in New Zealand comes from only a few sites in northern New Zealand. Coromandel is one of the source areas, and this glossy, translucent, tremendously sharp material forms a perfect knife edge when shattered. A quick scuttle around the Online Encyclopaedia of New Zealand revealed that flake tools such as the ones we found were used by Maori to scraping and chopping. The main site for obsidian at Mayor Island in Coromandel was the source of most obsidian traded throughout the country.

Another hand-crafted object from the former inhabitants of the island came to light, in our orientation walks around the island. A beautifully crafted adze was found on the surface of the soil, near the top of the island.

On discussion with Te Papa experts on early Maori objects, Dougal Austin and Pat Stodart, their view was that the adze had been made from Tahanga basalt, from the quarry on a nearby mainland Coromandel Site at Opito Bay (see map above). The wear on the adze (i.e. very little polishing) and the lack of sign of where it would have been lashed to the wooden haft (handle) indicates that the object was only partially finished before being lost or abandoned. They believe the lack of a hammerstone finish on the body of the blade indicates that it was unfinished. Pat’s suggestion for its condition is that it was brought to the island for finishing, and was partially broken during that process, and therefore abandoned. This view conforms with that of Ngati Hei kaitiaki – Joe Davis, on these objects, with many unfinished adzes found around the area. Similar finished objects from the Pacific Island and New Zealand are held in the Te Papa collections, and show how adzes of this type were fitted to their haft.

The  obsidian pieces and adze we found were left in the safe-keeping of Ngati Hei in Coromandel.

More recent human occupation has also left its mark on the island. We found several relics of the now extirpated rabbits, with skulls of two specimens still intact nearly 10 years after they were poisoned in a DOC/Community sponsored operation to restore the ecology of the island.

A third type of human activity at the island is the maintenance of a light house, which now holds pride-of-place on the high point of the island. The lighthouse has only been on this high spot for some decades. Formerly, a light house was situated on a high point at the rocky northern end of the island. A visit there one afternoon showed us that human occupation of any kind leaves its mark. Although the old light house is dismantled and only its foundation plinth remains, many shards of the thick glass from the lens, in angled shapes were scattered down the rocky slopes below. It might have had a Fresnel lens, like the one pictured below. Any readers that know more about the lighthouse out on the island might be able to fill us in on the details of what kind of light it had, or other information.

The final set of objects were of a less romantic or esoteric nature than hand crafted obsidian fragments or less evocative of mystery and isolation than light houses.

Marine debris are entirely a less appealing topic. And yet the lovely slopes of Ohinau Island are one of the sites most littered with small pieces of plastic of any small island around northern New Zealand (Buxton 2013). We encountered a high density of small plastic pieces, which were almost entirely blue or green in colour, had rounded edges, and were thumb-nail sized. Perhaps they had been ingested by the many seabirds nesting at Ohinau Island, accounting for their rounded edges, uniform small size and distribution in the midst of the bird colony.

Marine debris, as we’ve heard during the searches for lost flight MH370 are widespread throughout marine areas, even in the remotest parts of the ocean. In inhabited regions, plastic debris are particularly common. In the Bay of Plenty, with strong commercial and recreational fishery activity, and recent marine pollution events, plastic debris are a sad, but inevitable feature on our remote, and uninhabited islets. The effect of the plastics on seabirds is potentially damaging, and further investigation may be required to find out if they are a serious threat to the wellbeing of shearwaters at Ohinau Island. Both for shearwaters, as for other seabirds like albatrosses, petrels, plastic ingestion is a plague, reducing their ability to digest food leading to starvation in juveniles, and with potential to lead to hormonal effects, blocking reproduction in extreme cases. Flesh-footed shearwaters studied at Lord Howe in Australia also ingest a large amount of plastic debris, and a higher level than other marine vertebrate species studied (Lavers et al. 2014). While the Ohinau Island plastic debris is on a light scale compared to other areas in the Pacific, its presence is a reminder to be vigilant about how we manage waste, and to minimise our effects on the environment, lest we upset the delicate balance of nature.