Re Mount

Tasmanian coastal saltmarsh community transitions associated with climate change and relative sea level rise 1975–2009

Coastal saltmarshes are reputed to be one of the most vulnerable communities to global warming, with widespread evidence of retreat and movement of lower marsh vegetation into areas previously occupied by upper marsh vegetation in response to rising sea levels, and potential changes in community composition from changes in rainfall, temperature and wind. We undertook an investigation of decades scale change in the distributions of saltmarsh communities defined by dominant species, using historic vegetation maps, remote sensing imagery and extensive field data collection. Our study area in south-eastern Tasmania has suffered a marked increase in temperatures and wind speeds and a marked decrease in rainfall since 1975, with sea level rising at a rate of 0.8 mm per annum. We therefore tested the hypothesis that these changes would result in a shift in saltmarsh community composition towards more salt- and inundation-tolerant communities and salt scalds. Eighteen percent of the 1975 marsh was lost to direct human modification and a net 4% was lost to coastal retreat. One large marsh was cut off from the sea then burned, then reconnected with the sea. The vegetation change between 1975 and 2009 in other parts of the saltmarshes occurred in 21% of their 1975 area. Most of the community transitions were consistent with increasing aridity. Thus, our results indicate that global warming has already caused marked changes in community composition in saltmarsh in Tasmania.

Environmental reporting and accounting in Australia: progress, prospects and research priorities.

Despite strong demand for information to support the sustainable use of Australias natural resources and conserve environmental values and despite considerable effort and investment, nation-wide environmental data collection and analysis remains a substantially unmet challenge. We review progress in producing national environmental reports and accounts, identify challenges and opportunities, and analyse the potential role of research in addressing these. Australias low and concentrated population density and the short history since European settlement contribute to the lack of environmental data. There are additional factors: highly diverse data requirements and standards, disagreement on information priorities, poorly measurable management objectives, lack of coordination, over-reliance on researchers and businesses for data collection, lack of business engagement, and short-term, project-based activities. New opportunities have arisen to overcome some of these challenges: enhanced monitoring networks, standardisation, data management and modelling, greater commitment to share and integrate data, community monitoring, increasing acceptance of environmental and sustainability indicators, and progress in environmental accounting practices. Successes in generating climate, water and greenhouse gas information appear to be attributable to an unambiguous data requirement, considerable investment, and legislative instruments that enhance data sharing and create a clearly defined role for operational agencies. Based on the analysis presented, we suggest six priorities for research: (1) common definitions and standards for information that address management objectives, (2) ecological measures that are scalable from local to national level, (3) promotion of long-term data collection and reporting by researchers, (4) efficient satellite and sensor network technologies and data analysis methods, (5) environmental modelling approaches that can reconcile multiple data sources, and (6) experimental accounting to pursue consistent, credible and relevant information structures and to identify new data requirements. Opportunities exist to make progress in each of these areas and help secure a more sustainable future.

Acquisition of Through-water Aerial Survey Images: Surface Effects and the Prediction of Sun Glitter and Subsurface Illumination

The behavior of light at the air/water interface has substantial effects on the quality of vertical, or nadir-looking imagery used to interpret subsurface features for purposes such as marine habitat mapping. Reflection of the direct solar beam into the sensor by waves on the surface of the water creates bright glints, which obscure bottom features of interest. Sun angle, refraction, and reflection of the direct solar beam affect the amount of subsurface illumination and shadowing of bottom features. Simple interpretations of these sea surface effects are made with sufficient accuracy to improve planning for airborne, vertical image capture, particularly aerial photography or video imagery. The time available for image capture over shallow water is typically limited to a short period in the morning. The start time is controlled by subsurface illumination levels, which are determined by sun angle and locally variable factors, such as light attenuation by the water column, rather than surface reflection or subsurface shadowing. The end time is determined by sun glitter effects, which in this case study, are predictable from sun angle, camera field of view, and wind speed with an R 2 value of 0.9554.

Rapid monitoring of extent and condition of Seagrass habitats with aerial photography “mega‐Quadrats”

Monitoring seagrass habitats is required by many agencies and jurisdictions including Natural Resource Management (NRM) regions in Australia. Baseline mapping of seagrass habitats is proceeding in Tasmania, Australia and the next stage will be to conduct regular monitoring of extent and condition. This paper presents a summary of the results of recent research that addressed outstanding issues in reliable measurement of seagrass condition with optical remote sensing. The results enable the proposal of a new monitoring methodology based on sampling habitats with “mega‐quadrats” (around 200 m x 200 m) extracted from “low tech” imagery and present a prototype image visualisation comparison matrix (IVCM).