#30DayMapChallenge · Day 13 · Interactions

Can a squirrel cross Hamburg without touching the ground?

Hamburg records every street tree: where it stands, how wide its crown is, its trunk and its species. 228,091 trees. Do they connect?

Explore the canopy network

Tap a tree or a park to see how far a squirrel gets from there.

Jump distance 2 m Main roads block the waycut every link that crosses a motorway, trunk, primary or secondary road Show real squirrel sightings1,057 red-squirrel records from GBIF, 2010–2026 Buildings 80%

Tap a tree or a park to see how far a squirrel gets from there.

One tree would join two islands · tap to plant it

Does jumping further help?

Data, method and limits

Trees. Hamburg's street-tree register (Straßenbaumkataster): every tree on public streets with a recorded crown diameter, 228,091 of 229,013. Position, crown width, trunk circumference, species and planting year come from the register. Tree heights are not in the register and are estimated from crown width; crown shapes follow species and cultivar.

Links. Two crowns are linked if they touch, or, with jumping, if the gap is at most the chosen distance (2 m is an assumption to compare, not a measured squirrel jump). Crowns reaching a park, cemetery or allotment (Digitaler Grünplan) link to it; those areas count as safe ground.

Main roads. With the switch on, a link whose straight line crosses a major road (OpenStreetMap) is cut. Crowns can meet above a road, so this is a stricter scenario.

New trees have an 8 m crown. The five suggested trees are chosen one by one to lengthen the longest path the most, with gaps of 2 m or less and never across a major road.

Sightings. Red squirrel (Sciurus vulgaris) human observations in Hamburg from GBIF, 2010–2026, location uncertainty 100 m or less, open licences (CC0, CC BY, CC BY-NC). Sightings show where people noticed and reported squirrels, not everywhere squirrels live. Private gardens and trees inside parks are not in the tree register.

Limits. Circles are not branches; a link is a possible path, not an observed squirrel.

Trees and green areas © Freie und Hansestadt Hamburg, BUKEA (dl-de/by-2-0) · sightings via GBIF.org (naturgucker, iNaturalist, observation.org and others; see data/sightings.json) · roads and buildings © OpenStreetMap contributors (ODbL), buildings via OpenFreeMap · basemap © CARTO · Barış Parlatangiller, built with Claude · code · all maps

long canopy chainshort chain no neighbour in reachreachable squirrel seennew tree park · cemetery · allotment