Species on the move around the Australian coastline: A continental-scale review of climate-driven species redistribution in marine systems

Abstract

Climate-driven changes in the distribution of species are a pervasive and accelerating impact of climate change, and despite increasing research effort in this rapidly emerging field, much remains unknown or poorly understood. We lack a holistic understanding of patterns and processes at local, regional and global scales, with detailed explorations of range shifts in the southern hemisphere particularly under-represented. Australian waters encompass the world's third largest marine jurisdiction, extending from tropical to sub-Antarctic climate zones, and have waters warming at rates twice the global average in the north and two to four times in the south. Here, we report the results of a multi-taxon continent-wide review describing observed and predicted species redistribution around the Australian coastline, and highlight critical gaps in knowledge impeding our understanding of, and response to, these considerable changes. Since range shifts were first reported in the region in 2003, 198 species from nine Phyla have been documented shifting their distribution, 87.3% of which are shifting poleward. However, there is little standardization of methods or metrics reported in observed or predicted shifts, and both are hindered by a lack of baseline data. Our results demonstrate the importance of historical data sets and underwater visual surveys, and also highlight that approximately one-fifth of studies incorporated citizen science. These findings emphasize the important role the public has had, and can continue to play, in understanding the impact of climate change. Most documented shifts are of coastal fish species in sub-tropical and temperate systems, while tropical systems in general were poorly explored. Moreover, most distributional changes are only described at the poleward boundary, with few studies considering changes at the warmer, equatorward range limit. Through identifying knowledge gaps and research limitations, this review highlights future opportunities for strategic research effort to improve the representation of Australian marine species and systems in climate-impact research.

Keywords: citizen science; climate change; ecosystem reorganization; historical data; ocean warming; range contraction; range extension; range shift.

FIGURE 1

Changes in mean summer and winter sea surface temperature surrounding Australia from 1982 to 2018 based on 5‐year means centred on 1984 and 2016 (upper panels) and corresponding time‐series for four geographically explicit regions (a–d) of Australia's surrounding ocean. Trends in sea surface temperature data are presented for summer (red lines), autumn (orange lines), winter (blue lines) and spring (green lines) annual averages from each region. Data source: Daily global sea surface temperature reprocessed (level 4) from the Operational SST and Ice Analysis system (OSTIA), downloaded from the Copernicus Marine Environment Monitoring Service (https://marine.copernicus.eu; product #010_011)

FIGURE 2

Temporal trends in observed Australian marine range shift literature. Bars represent the number of publications per year and colours represent the varied data sources that studies have used to observe and verify species range shifts

FIGURE 3

Species representation and spatial distribution of observed range shifting species across Australia. Circles represent number of species per class observed shifting by region (different border patterns) in Australia. Phyla are represented by different colours

FIGURE 4

Each dot represents the number of species observed undergoing a specific range shift as well as the diversity of observed shifts in the literature. Arrows (or bar) represent both the range edge observed (equatorward or poleward), as well as the direction of the shift (extension, contraction or no observed shift). Arrows outlined in black denote the climate‐driven species redistributions that are consistent with the environmental effects of climate change. Please note that the y‐axis is not continuous, as the number of observations of poleward extensions in Tasmania are more than double the next greatest category (Western Australia poleward contractions). The total number of species shifting per region are indicated at the top and the number of species not observed shifting are in parentheses

FIGURE 5

Bar graph depicting the rate of range shifts (km dec⁻¹ ± SEM) of marine species across Australia both poleward, consistent with the environmental effects of climate change (solid bars within the shaded boxes) and equatorward (opaque bars). Colours represent different taxa: invertebrates (purple), algae (green) and fish. The numbers above/below each bar represent the number of species contributing to each bar. Please note that the y‐axis is not continuous