Social–environmental drivers inform strategic management of coral reefs in the Anthropocene

Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages—the foundation species of coral reef ecosystems. Here, we compiled coral abundance data from 2,584 Indo-Pacific reefs to evaluate the influence of 21 climate, social and environmental drivers on the ecology of reef coral assemblages. Higher abundances of framework-building corals were typically associated with: weaker thermal disturbances and longer intervals for potential recovery; slower human population growth; reduced access by human settlements and markets; and less nearby agriculture. We therefore propose a framework of three management strategies (protect, recover or transform) by considering: (1) if reefs were above or below a proposed threshold of >10% cover of the coral taxa important for structural complexity and carbonate production; and (2) reef exposure to severe thermal stress during the 2014–2017 global coral bleaching event. Our findings can guide urgent management efforts for coral reefs, by identifying key threats across multiple scales and strategic policy priorities that might sustain a network of functioning reefs in the Indo-Pacific to avoid ecosystem collapse

Modelling the risk of cyclone wave damage to coral reefs using GIS: a case study of the Great Barrier Reef, 1969–2003

Tropical cyclones (hurricanes and typhoons) produce high winds that can generate waves capable of damaging coral reefs. As cyclones frequently pass through northeast Australia's Great Barrier Reef (GBR), it is important to understand how the spatial distribution of reef damage changes over time. However, direct measurements of wave damage, or even wave heights or wind speeds, are rare within the GBR. An important factor in estimating whether cyclone damage was possible is the magnitude and duration of high-energy wind and waves. Thus, before the spatio-temporal dynamics of past cyclone damage can be modelled, it is necessary to reconstruct the spread, intensity, and duration of high-energy conditions during individual cyclones. This was done every hour along the track taken by each of 85 cyclones that passed near the GBR from 1969 to 2003, by implementing a cyclone wind hindcasting model directly within a raster GIS using cyclone data available from the Australian Bureau of Meteorology. Three measures of cyclone energy (maximum wind speed-MAX, duration of gales-GALES, and continuous duration of gales-CGALES) were derived from these data. For three cyclones, where field data documenting actual reef damage from cyclone-generated waves were available, the predictive ability of each measure was assessed statistically. All three performed better in predicting reef damage at sites surveyed along the high-energy reef front than those surveyed along the more protected reef back. MAX performed best for cyclone Joy (r2 = 0.5), while CGALES performed best for cyclones Ivor (r2 = 0.23) and Justin (r2 = 0.48). Using thresholds for MAX and GALES obtained via comparison with field data of damage, it was possible to produce a preliminary prediction of the risk of wave damage across the GBR from each of the 85 cyclones. The results suggest that while up to two-thirds of the GBR was at risk from some damage for 30–50% of the time series (~18 out of 35 years), only scattered areas of the region were at risk more frequently than that

Tropical cyclones in the Great Barrier Reef, Australia, 1910-1999: first step towards charterising the disturbance regime

The proximity of a reef to a tropical cyclone path is the simplest means of estimating the potential for disturbance (that is, physical damage from waves) at that reef. Calculated for cyclones that tracked across a sample of reefs spanning much of the Great Barrier Reef (GBR) from 1910 to 1999, such proximities provide a preliminary history of cyclone disturbance in that region for which spatial and temporal trends can be examined. As the long-term dynamics of cyclone disturbance affect the structure and function of coral reef communities, the disturbance regime can be used to consider whether the current state of coral communities (as measured in 1999) represents that which was present over the entire time series, and whether the frequency of cyclone disturbance across the GBR is high (limited recovery time between events) or intermediate (variable recovery time between events) in nature. This analysis reveals that for more than half of the GBR, the latest major disturbance occurred less recently than normal for the time series (current communities had more time for recovery than usual) and that these disturbances are generally intermediate in frequency. However, because many factors other than distance affect the potential for disturbance, these results represent a first step towards characterising the nature of cyclone disturbance across the GBR

A geographic information systems model for mapping risk of fasciolosis in cattle and buffaloes in Cambodia

A geographic information systems (GIS) model for mapping the risk of fasciolosis in cattle and buffaloes was developed for the Kingdom of Cambodia using determinants of inundation, proximity to rivers, land use, slope, elevation, and the density of cattle and buffaloes. Determinants were subjectively weighted according to their perceived relative importance before combining them to produce a risk-map of fasciolosis. The model estimates that 28% of Cambodia is potentially at risk of fasciolosis with areas of high and moderate risk concentrated in southern and central Cambodia. The estimates of risk reflect the actual prevalence of fasciolosis in most districts surveyed, suggesting that the epidemiological determinants and weightings used to produce the model were appropriate. These results will be progressively refined as more detailed field surveys are completed to fully validate the model

Validation of a geographic information system model for mapping the risk of fasciolosis in cattle and buffaloes in Cambodia

Maps showing gradations of risk of fasciolosis due to Fasciola gigantica in Cambodia were produced using geographic information systems (GIS) technology in conjunction with determinants of fasciolosis. A comparison between levels of risk predicted by the maps and field measurements of prevalence in 11 provinces (n = 1406) showed general agreement, which suggested the epidemiological determinants and weightings used to produce the maps were appropriate. However, due to logistical constraints, prevalence was measured at the provincial level and animals were not randomly sampled (and thus were unlikely to be representative of variability within provinces). To address this, additional field work was carried out to measure prevalence in more detail—faecal samples were collected from a randomly selected set of animals in four districts across a representative province for areas predicted to be at high risk (n = 311), moderate risk (n = 268) and no risk (n = 262). As with the original field survey, the results show general agreement between prevalence and risk predicted by the maps, with the best fit found for areas predicted to be at high risk

The state of Western Australia’s coral reefs

Western Australia’s coral reefs have largely escaped the chronic pressures affecting other reefs around the world, but are regularly affected by seasonal storms and cyclones, and increasingly by heat stress and coral bleaching. Reef systems north of 18°S have been impacted by heat stress and coral bleaching during strong El Niño phases and those further south during strong La Niña phases. Cumulative heat stress and the extent of bleaching throughout the northern reefs in 2016 were higher than at any other time on record. To assess the changing regime of disturbance to reef systems across Western Australia (WA), we linked their site-specific exposure to damaging waves and heat stress since 1990 with mean changes in coral cover. Since 2010, there has been a noticeable increase in heat stress and coral bleaching across WA. Over half the reef systems have been severely impacted by coral bleaching since 2010, which was further compounded by cyclones at some reefs. For most (75%) reef systems with long-term data (5–26 yrs), mean coral cover is currently at (or near) the lowest on record and a full recovery is unlikely if disturbances continue to intensify with climate change. However, some reefs have not yet experienced severe bleaching and their coral cover has remained relatively stable or increased in recent years. Additionally, within all reef systems the condition of communities and their exposure to disturbances varied spatially. Identifying the communities least susceptible to future disturbances and linking them through networks of protected areas, based on patterns of larval connectivity, are important research and management priorities in coming years while the causes of climate change are addressed