By Fiona Hodge

The onset of summer brings sunshine, sunscreen lotion, and often sun burn. New Zealand lies close enough to the ozone hole that our burn times are low, and our skin cancer rates are high. This year brings some small relief: NIWA have predicted the hole in the ozone layer, our UV shield, to be smaller this year than in previous years.

The hole in the ozone layer was created mainly by refrigerant chemicals (CFCs) released into the atmosphere until the late 1980s. The size of this hole varies every summer, due to a combination of complicated climatic factors and the slow recovery of the ozone layer.

This hole has resulted in high levels of high energy UV rays for New Zealanders, including New Zealand plants and animals. UV rays can cause mutations in the DNA of cells, which can lead to cancers. They can also damage other cell components. Amongst us humans some will be more at risk than others due to differences in lifestyles, behaviour, and genetics. This too is true for our flora and fauna.

Life cycles determine the exposure the vulnerable young get to UV light. Animals that have a long larval stage in full sunlight are particularly vulnerable. Many marine species, including fish, have transparent larvae that live in the surface of the sea – fully exposed to UV rays. Embryos are particularly sensitive to UV damage during development, and tend not to be equipped with pigments or adaptations to avoid or reduce exposure.

Plants and animals that avoid direct sunlight will be less exposed to UV. However, many organisms have not yet adjusted their behaviours, which were adapted for lower UV environments (before the ozone hole). For example small intertidal snails lay egg cases in the intertidal, often in direct sunlight, exposing them to long periods of UV light during their most sensitive life stage.

Sun-screen like compounds have been found in a wide variety of plants and animals, ranging from mosses to plankton to seaweeds to corals to humans (melanin). These compounds are able to safely absorb the energy from the UV rays, preventing it from doing damage to the cell. The presence of these varies, again making some species and individuals less vulnerable than others.

Despite the behavioural and lifestyle adaptations many of us humans have (think slip, slop, slap and wrap), the smaller than usual ozone hole will be a relief. Even more so for animals and plants less equipped to avoid the UV damage. It’s also a tantalising taste of what’s to come: “In the future we expect [ozone] to recover,” says Dr Morgenstern of NIWA. However he also warns against premature excitement “There is no sign of the ozone hole shrinking nor is there any significant recovery just yet”.