S6E5: Don’t Count Trees; Count Crowns with Jan Willem de Groot of Terra Nostra

Amsterdam’s trees haven’t “stopped growing” — they’ve stopped growing the way they should. Arborist-turned-CEO Jan Willem de Groot explains why maturity matters more than planting counts, why crown volume is the metric that actually reflects ecological function, and what happens when cities focus on keeping the trees they already rely on. We explore why large trees provide exponentially more shade, cooling, habitat, and carbon storage than saplings; how risk-averse maintenance has erased vital hollows and “imperfections” that wildlife depends on; and why the real frontier of the urban forest is private land, where most canopy sits and most removals happen. Jan Willem shares how Terra Nostra and greehill are using LiDAR-based smart inventories to create accurate, city-wide digital twins — not to replace arborists, but to free them to focus where their expertise matters most. We also talk about Ukraine’s lanes of heroes — memorial trees that carry names, grief, and continuity — and what they teach us about trees as living memory, not just infrastructure. Technology can help us see what is worth keeping. But meaning is what keeps it standing.