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