For this round-table, I’ll start by giving an overview of a number of topics around the fascinating field of coastal ecosystems and coastal risk reduction. I’ll give an update on the activities of the SNAP Coastal Defenses Working Group and my work within this group, touch upon a closely coastal hazards assessment exercise in Papua New Guinea and an upcoming project on mangrove restoration for coastal resilience. I would like to combine this talk with a discussion on the challenges of small data; of bringing together diverse disciplines to bear on a single issue and; of finding ways to tie these disparate strands together.
For a sneak preview, here is an outline of some results from an almost (but never) complete meta-analysis:
We synthesize global evidence from field measurements of wave and storm surge reductions in natural coastal habitats and data on the costs and benefits of habitat restoration projects targeted at coastal protection. 76 field measurements show that coastal habitats can reduce wave heights up to 79% (or wave energy up to 96%). Coral reefs are the most effective habitats for wave reduction, followed by salt-marshes, mangroves and seagrass and kelp beds. In addition to waves, coastal mangrove and marsh wetlands can reduce storm surge heights by up to 70% over extents of several kilometers. We find a strong relationship between incident wave heights and wave reduction extents for all habitat types. Other critical biophysical parameters that influence wave reduction include habitat width (coral reefs and seagrass/kelp) and vegetation height (mangroves, salt-marshes). We also discuss the influence of a few engineering ratios (e.g. the ratio of wave height H over water depth, h) on wave reduction extents. We conduct the first global review of the costs and benefits of past and on-going habitat restoration projects targeted at coastal protection. The projects provide a wide range of coastal protection and risk reduction benefits including reductions in erosion, flood damage and engineering costs. Quantitative assessments of benefit-cost ratios and comparisons to engineering structures suggest that mangrove projects are the most cost-effective and are, on average, twice as cheap as comparable engineering structures for wave reduction.
Hope to see you there!
John Sabo, a visiting researcher from Arizona State University, will be presenting this week’s roundtable! He will be telling us about his work in the ecologically and economically important Mekong River Basin. We will be continuing the climate change theme from last week’s talk, but moving onto its impacts on fisheries instead. He will also discuss how dams have impacted the river and fisheries.
Abstract: Inland capture fisheries on the Mekong River provide a majority of the animal protein and vitamin A to the diets of over 40M people in the Lower Mekong River Basin. The productivity of this fishery is fueled by the monsoon flood pulse which creates wetlands the size of small US states in Cambodia and Vietnam. The region is experiencing rapid development, including the planning and impending construction of over 20 hydropower facilities, some already built. Climate change will also likely change the intensity and timing of the South Asian Monsoon, with implications for the extent of the ensuing flood pulse and the fishery that depends on it. In this roundtable I will address two topics. First, I present the results from a century scale analysis of change in hydrologic variation and key aspects of the flood pulse on the Mekong River including an assessment of current dams. This analysis is done within a novel spectral framework that allows for identification of baseline stationarity and decomposition of the linear, seasonal and stochastic components of change in daily discharge. Second I link spectral measures of hydrologic variation to catch data from the fishery using a 15-year dataset of the Dai fishery on the Tonle Sap River (Cambodia) and a second time series approach—a multivariate autoregressive state space (MARSS) model. The spectral-MARSS framework is then used to forecast the fishery under near time climate change. Daily discharge variation and key aspects of the flood pulse have been experiencing natural change for over a century. Existing dams have modified discharge in spite of a shifting baseline. Fisheries catch varies with several spectral measures of daily discharge variation. Surprisingly, low flows have equal if not higher positive effect sizes than high flows on catch in this flood pulse system and spectral measures outperform “first moment” measures of flood pulse extent. Moreover, antecedent hydrology—the flood drought sequence from the previous 1-2 years—significantly affects current catch in the fishery. These results suggest that the spectral-MARSS framework may provide a robust tool for forecasting fisheries production in the future.
Ian McCullough is from the UCSB Bren school and will be presenting on his PhD research. Join us for this timely talk on climate change and California forests.
Co-author credits: Frank Davis, Lorraine Flint, Alan Flint, John Dingman
Abstract: Climate change has emerged as a potent threat to forests worldwide, resulting in heightened concern for the sustainability of timber resources, ecosystem services, structure and function. In this study, we investigate the effects of long-term climate change on the growth and distribution of ponderosa pine in the Sierra Nevada of California using tree-rings and statistically downscaled climate models. We focused initial efforts on a small, declining population at Tejon Ranch, near the species’ southern range limit. Subsequently, we incorporated published tree-ring chronologies from the International Tree-Ring Data Bank to assess climate-growth relationships along a Sierra Nevada latitudinal gradient. Climatic controls on growth have varied historically across the gradient. Although precipitation was the primary limiting factor at all sites, more northern sites were more sensitive to fall temperatures, whereas southern sites were more sensitive to climatic water deficits (measure of unmet evaporative demand for water). Given that trees cannot live where they cannot grow, we are currently exploring ways to use the climate-growth relationship to infer the potential future distribution of ponderosa pine based on locations of favorable growing habitat.
In December 2011, an important cultural and ecological process was reignited in Pinnacles National Park when the Amah Mutsun Tribal Band gathered alongside agency fire crews and land managers to burn a stand of native deergrass (Muhlenbergia rigens). Throughout California, California Indian people traditionally burned selected areas to manage and promote food and fiber. This project is unique in that it incorporates two distinct knowledge systems and welcomes an indigenous perspective in park research and management. From the project’s beginning, tribal partners participated in establishing research questions and goals of the project. Tribal members, and especially tribal youth, regularly participated in collecting data and implementing treatments. The burn is one of several highlights of this integrated program at Pinnacles that aims to gain a better understanding of California Indian management practices and its role in shaping the landscape over centuries of time, and how this awareness influences today’s management.
Park Botanist, Acting Chief
Research and Resource Management Division
Pinnacles National Park
Navigating working group dynamics can be challenging but is a necessary step to achieve synthesis. Here we discuss hurdles to synthesis and navigating collaborations in working groups (e.g. data availability and integration, analysis techniques, and social / collaborative issues). We will start with a brief informal presentation of key elements of the issue, and aim to spend most of the time engaged in discussion with the NCEAS community. Please come prepared to discuss a hurdle to synthesis (and/or solution!) which you have experienced.
Rachael Blake, NCEAS Post Doc
Jessica Couture, NCEAS Research Associate
Colette Ward, NCEAS Post Doc