Turning up the heat on global hotspots of marine biodiversity

Ramírez (1, 2), I. Afán (3), L. S. Davis (4) and A. Chiaradia (2)

(1) Department of Wetland Ecology, Estación Biológica de Doñana (EBD-CSIC), Sevilla, Spain; (2) Research Department, Phillip Island Nature Parks, Victoria, Australia; (3) Laboratorio de SIG y Teledetección (LAST-EBD), Estación Biológica de Doñana (EBD-CSIC), Sevilla, Spain; (4) Centre for Science Communication, University of Otago, Dunedin, New Zealand.

Climate change is a fact of life. Indeed, the year 2016 has been the hottest on record, reflecting a generally rising trend in the Earth’s temperature. But, is this trend the same everywhere around the world? Understanding the global distribution of these changes is extremely important to be able to assess the threats that local ecosystems must face. The challenge is how to approach the spatial distribution of climate-driven environmental changes in an environment as remote, vast and inaccessible as the ocean. This challenge was taken up by scientists from Spain, Australia and New Zealand in a paper published in Science Advances. Interestingly, satellite remote-sensing records are readily available for us to look at our planet from the right perspective, informing on the most recent and striking trends and patterns in both environmental and biological variables in the world’s oceans. Accordingly, the research team took advantage of data gathered over more than 30 years from a whole constellation of satellites orbiting our planet and imaging its surface for determining how the temperature, productivity and currents of our oceans have changed over the last three decades, down to within just a few kilometres. Rather than the magnitude of environmental changes, it is important to note the uneven distribution of environmental changes, which hugely vary from the local to the regional scales (Fig. 1). Indeed, there are places where the temperature increase and associated environmental changes have been much greater than elsewhere. For instance, the North Sea, between America and Europe, and all the marine areas connected by the Labrador Current have experienced one of the largest global increases in ocean temperature. Similarly, some water masses of the North-Pacific Ocean Basin, from the Bering to the East China Seas, or of the Southern Ocean, between Australia and New Zealand, have also recorded large increases in ocean temperature with consequent decreases in marine productivity. Accordingly, we should expect that consequences of changing climatic variables will be site-specific. Similarly, to the observed changes in oceanographic features, marine species are also heterogeneously distributed. This begs the question: are environmental stressors affecting marine areas of enhanced biodiversity? Based on the worldwide distribution of more than 2,000 marine species, the research team identified up to six hot spots of marine biodiversity that concentrate in the Southern Hemisphere and include marine areas in temperate and tropical regions of the Atlantic, Indian and Pacific Oceans (Fig. 2). Overall, all these areas have experienced environmental perturbations, but again, a large degree of spatial variability in such environmental impacts was also observed within these hot spots. Whereas some species may benefit from shifts towards environmental conditions outside the normal range of variability, in most cases, however, such environmental changes will prove suboptimal and this will be made apparent through changes to populations and communities (Video 1). The overall picture of human-related impacts on the marine environment would be incomplete without consideration of industrial fisheries. Albeit coarser than our estimates of climate impacts and distribution of marine biodiversity, available industrial fishery data suggest a worrying coincidence whereby the world’s richest areas for marine biodiversity are also those areas being impacted most from both climate change and industrial fishing. Although biodiversity conservation is an issue of global concern, fishing policies are most commonly derived from decisions taken at a national level. It behoves the international community, then, to find solutions that go beyond the interests and borders of sovereign states if we are to conserve the biodiversity in these marine hotspots, in a similar way to which the world must tackle the associated causes of climate change itself. This study contributes to the international effort to mitigate the causes and consequences of climate change.

Citation: F. Ramírez, I. Afán, L. S. Davis, A. Chiaradia (2017). Climate impacts on global hot spots of marine biodiversity. Sci. Adv. 3, e1601198 (2017).

Figure 1. Global trend in water temperature. Colours denote the rate at which changes in water temperature have occurred, with red colours indicating areas with the highest increasing rates.


Figure 2. Global distribution of marine biodiversity. Colours denote the number of species, with red colors indicating areas with the highest biodiversity.

Video 1. The little penguin (Eudyptula minor) could be a “nice” example of a species potentially affected by such environmental changes. Little penguins are distributed along the south coast of Australia and New Zealand. This area matches with one of the proposed marine hot spots and is particularly impacted by increasing water temperatures. This video taken by a camera onboard a little penguin shows us how this species interact with its environment: https://www.dropbox.com/s/u45muz2glkawpia/penguin%20dive%20Science%20Advances.mp4?dl=0