1.5 million downloads of the dataset that tracks every new road, rooftop, and parking lot on Earth — 30 meters at a time, across 36 years of relentless expansion.
Impervious surfaces are the most permanent mark humanity leaves on the landscape. Forests can be replanted. Farmland can be restored. But once soil is sealed beneath concrete or asphalt, it almost never returns. GISA captures this one-way transformation at 30-meter resolution across the entire planet from 1985 to 2021 — a period during which the total impervious surface area on Earth roughly doubled. Every new highway interchange, every suburban housing development, every industrial park that replaced rice paddies on the outskirts of Guangzhou or corn fields outside São Paulo is recorded in this dataset as a pixel that flipped from pervious to impervious and stayed that way.
The 30-meter resolution — derived from the Landsat satellite archive — is what sets GISA apart. At this scale, individual city blocks are visible. Researchers can distinguish between a dense urban core and a low-density suburban fringe. They can track how a city grows: does it densify inward or sprawl outward? The answer varies dramatically by region. Chinese cities tend to build upward, sealing relatively compact footprints at high density. American and Australian cities spread laterally, consuming far more land per capita. GISA makes these patterns quantifiable, not just anecdotal.
The dataset's 1.5 million downloads make it the most accessed land-cover product on Zenodo by a wide margin. Its users span hydrology (impervious surfaces drive stormwater runoff), urban heat island research (sealed surfaces absorb and re-radiate solar energy), biodiversity conservation (habitat fragmentation follows road networks), and climate modeling (surface albedo changes affect local and regional temperatures). What unites these fields is a shared recognition that the boundary between pervious and impervious is one of the most consequential thresholds in Earth system science — and GISA is the most detailed record of where and when that threshold was crossed.
Total impervious surface area worldwide in thousands of square kilometers, showing accelerating urban expansion
Every new square kilometer of impervious surface eliminates natural infiltration, increasing stormwater runoff volume. GISA enables hydrologists to quantify exactly how much additional runoff each year of urbanization has produced in any watershed on Earth.
Sealed surfaces absorb solar radiation and re-radiate it as heat, creating urban heat islands that can be 5-10°C warmer than surrounding rural areas. GISA's temporal depth reveals how heat islands have expanded and intensified over 36 years.
Roads and built surfaces fragment natural habitats into isolated patches. Conservation biologists use GISA to map connectivity corridors and identify where remaining habitat is most threatened by approaching urbanization fronts.
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