September 19, 2016

GIS and Mapping

LiDAR & Mapping:

LiDAR is the process of surveying distance with the use of high powered lasers. In the context of environmental science we are developing a small LiDAR package to create 3D models and maps for use in quantitative analysis. These models are generally highly accurate and can be compared against each other over time as well as used in simulations such as fluid volume simulations on riverbeds and erosion projections on cliff sides. We also use 2D image mapping from aerial photos to create larger high resolution 2D maps. Using a program known as Pix4D we can turn these 2D mapping images into 3D colorized point clouds as well and it is our hope to compare our LiDAR solution and the photogrammetry of this program.
With these techniques we can make serious headway in geomorphology studies in our area of influence.


Alumni Ryan Summers

The effect of removing non-native grazers from Santa Rosa Island: 25 years of vegetation change


Human use of Santa Rosa Island (SRI) dates back 13,000 years, starting with the island Chumash before ranching was introduced in 1843. Intensive grazing by non-native ungulates impacted native woodland, chaparral, and scrub vegetation, introduced European annual grassland species, and triggered large-scale erosion.  Following creation of Channel Islands National Park in 1986, non-native grazers were removed to restore native vegetation. Sheep had been removed from SRI by the early 1900s, and feral pigs were removed by 1992, cattle by 1998, and introduced deer and elk by 2010. We evaluated the long-term vegetation change following grazing cessation through analysis of a time series (1991 - 2015) of Landsat TM5 and Landsat 7 satellite images.  The images were processed with a maximum likelihood classification using regions of interest (ROIs) delineated from current and historical photographs, Channel Island National Park inventory and monitoring records, and ground truthing.  We also conducted a terrain analysis using a 1-m resolution Digital Elevation Model from the National Park Service, using slope steepness, curvature, and aspect to evaluate the influence of grazer accessibility.  Scrub, island chaparral, and woodland cover has significantly increased, and valley and foothill grassland and bare ground cover has significantly decreased.  There was a significantly higher percent change on gentle slopes (<10%) and moderate slopes (10-30%) compared to steep slopes (>30%). Results indicate that passive restoration has occurred on extensive areas of SRI, with the highest percent change in areas previously accessible to non-native grazers. However, there may be limits to passive restoration, with 7.9 km2 of bare and eroded areas on highland ridges that are not undergoing succession. Future studies will analyze the environmental conditions that make bare and eroded areas resistant to vegetation change, including potential synergistic effects of slope steepness, curvature (convex vs. concave slopes), solar isolation, and wind exposure.


Alumni Vanessa van Heerden

Assessing the health of coral reef ecosystems in an era of anthropogenic stressors at Aitutaki, Cook Islands


Aitutaki, Cook Islands, is an almost-atoll with a large inhabited island, surrounded by a barrier reef and many uninhabited motus (islets). Being located in the center of the South Pacific, this island is at the epicenter for many oceanic circulation currents, permitting the establishment and resilience of diverse biotic communities. Coral reefs are a vital marine resource for Cook Islanders, yielding a variety of sustenance, supporting sustainable tourism, and providing coastal protection. Aitutaki’s reefs are subject to a number of threats including fishing pressure, poor water quality from land runoff, and the presence of marine debris. To assess the current status of Aitutaki’s reefs, the coral reef communities were surveyed and characterized at 12 sites including parameters such as the substrate type, invertebrate, and fish assemblages. The sites were chosen around the entire main island and near motus on the barrier reef. The terrestrial activities that occur on and around the island of Aitutaki, including agriculture runoff, the use of DDT, and overfishing of target fishery species has an adverse effect on the health of coral reefs, as denoted by the abundance of sea cucumbers (p<0.001) on reefs adjacent to the inhabited island and the difference in species richness of fish between motu and island sites (p<0.01). In comparison to other reef ecosystem health indices, Aitutaki’s reefs are in poor health compared to global standards, with the majority of reefs falling within a 1 or 2 rating (2=Poor, 1=Critical). Based on mortality indices, the future of Aitutaki’s reefs are in need of protection from “take”. In a world overrun by humans, small nations like Aitutaki are challenged to balance ecological preservation and economic gain. This project highlights reef resilience to anthropogenic influences and the most viable steps to provide for a successful future, both for the coral reef communities and the people of Aitutaki.