Next time you go for a walk in a forest or woodland take a moment to gaze above you. You might find that the canopy resembles a breathtaking umbrella of vivid-green crazy paving with channel-like gaps between the tops of the trees. Visually stunning, the phenomenon has been documented worldwide since the 1920s, and is called ‘crown shyness’. It happens when trees, usually of the same species but not always, appear to give each other space. Each tree crown is perfectly outlined in a halo of light, as though the whole canopy has shattered.
No one really knows why this happens. Scientists have theorised that trees can sense when they’re approaching a neighbour and halt their growth to ensure optimal light for photosynthesis. Another hypothesis is that the gaps prevent branches from getting damaged in the wind – although one study found that the spectacle didn’t appear to be more common in windier areas. It’s also possible that trees keep a respectful distance from each other to prevent the spread of pests and disease.