It’s no accident that marine turtles and seabirds choose to nest on remote islands. A secure place to raise young and access to a dependable source of food are essential elements for life. It’s not so different to ourselves. We choose houses in places with local services, that suit our needs.

The warm waters of the East Australian Current, that drives most of the coastal economies of eastern Australia, begins near Lihou. The current itself however, is very nutrient-poor, as are most tropical waters. The species that occur here must be able to find food, particularly during critical times of year. There is only so far that a turtle can swim and most seabirds, whilst they raise very young chicks, are restricted to only a one day flight from the nest.

The cycles of El Nino are a strong factor in the availability of food. Ironically, the nutrient-poor status of tropical waters can improve the chance of finding food, as what little is available for the pelagic (open water) food chain is concentrated along fronts, where different water masses meet. This might be the boundary between warmer and cooler water patches or, commonly, the upwelling zones around islands where animals nest.

Currents, tides and wind all serve to drag surface waters but if it is moved, water from elsewhere has to fill its place. If there is an island in the way, the only water available is from deep below. Over millenia, surface plankton has rained down to the deep sea bed so upwellings convey small particles back to the surface. Added sunlight promotes the growth of algae, which is grazed by zooplankton and then fish. So the nutrients this cooler water brings from the depths is vitally important. Nevertheless, the system is finely tuned and diversity, as is so often the case in nature, is found in the places with very little nutrient. With so much competition for space and resources, animals and plants have developed unique adaptations and communities are extremely rich.

There are potentially serious consequences of climate change for these ocean systems, which not only support seabirds and turtles but promote life around the world. The availability of surface nutrients is dependent on the strength of upwellings and warming ocean surfaces provide less and less. Small changes make a big difference and coastal fisheries, turtle breeding and seabird chick production are all dependent on the weather. Changing or altering the intensity of the boundary effects will have profound effects on wildlife survival. If we begin to lose these species, it will be a sign of serious ecosystem failure, and the human welfare consequences could be disastrous. Our lives are integrally connected to the ocean and what is going on here at Lihou is a mere reflection of what’s happening all around the world.