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30 year global surface water change: Implications for aquatic diversity
Kalacska M., Lucanus O., Arroyo-Mora J.P.
Context• Freshwater ecosystems are among the most threatened on Earth
• Freshwater fish comprise one-fourth of living vertebrates (> 15,000 species)
• ~200 new species are still being described every year
• BUT information about their populations, conservation status and response to climate/human-induced change acutely incomplete and inaccurate
• Major systematic drivers of aquatic species loss include land cover and land use change (LUCC), overexploitation, invasive species, and climate change (micro habitats)*
Remote sensing can provide an unbiased historical assessment of habitat change, current estimates of habitat extent and diversity – and
be a monitoring tool
A Straightforward Question…(?)
• How much habitat loss or gain has there been over time for freshwater fish habitats?– Need to know: distribution of species and changes in
extent of surface water– Databases/catalogues of fish species fairly well up to
date (Fishbase, Catalogue of Fishes)• Geolocation and ranges imprecise/unknown for many
species
– In January 2016, no fine-scale multi-temporal, global scale dataset of surface water extent was available
• Focus on the Family Cichlidae• 1693 described species as of May 2017, with many new species yet to be
described
• Cichlids are distributed exclusively in tropical fresh water
• Have colonized most major bodies of water, and share these habitats with a great diversity of other aquatic species
• Many have limited ranges and high levels of specialization and/or endemism• Good indicators for overall aquatic habitat degradation from LUCC and
climate change
• Solution -> Assign all 1693 described species to freshwater ecoregion
Global Alpha Diversity of Cichlids
Network Analysis of Species Similarity per FWER
Which of these FWER are the most diverse? Which are the most threatened? Which have the highest level of endemism?
How much surface water is there?
How much has it changed over time?
Global Datasets
None have an adequate temporal and/or spatial resolution.
Landsat Collections
• Objective was to create multi-temporal global surface water layers
• 148 Ecoregions with cichlids– Avg: 61 images/region OLI = 9028– Avg: 66 images/region ETM = 9768– Avg: 34 images/region TM = 5032– Total: 23,828 images
• 426 Ecoregions total– OLI: 25,986 images– ETM: 28,116 images– TM: 14,484 images– Total: 68,586
Example from the Amazon River
Surface Water
50,000 km2 Area including the Ucayali and Napo Rivers in Peru
Conservation Case Study - Madagascar
94 endemic species
Comparison between different datasets
Very large discrepancies!
Endemic Fish Distribution
Results
• Critically endangered species found in 21% of Madagascar’s surface water (0.35% protected)
• Endangered species found in 18% of Madagascar’s surface water (2.5% protected)
• Endemic species found in 60% of Madagascar’s surface water
• Decrease in habitat of endemic, endangered, critically endangered species
• Negligible protection for freshwater habitats
Conclusions
• Surface water data readily extractable from remotely sensed imagery
• Yearly assessments allow for visualizing inter-annual patterns
• Historical imagery provides long-term trends• Accurate habitat extent is critically important
for conservation