In reply to wbo2:
> On a serious note I'd like to see a bit of effort on the chalk manufacturers to promote good, coloured chalks
The article linked in the OP is about more than just the visual impact of chalk:
"Beyond the visual pollution, new research suggests chalk may be harming the flora that grows on rocks. The latest study on the effects of climbing chalk, released October 2020, found that it negatively impacted both the germination and survival of four species each of rock-dwelling ferns and mosses in laboratory settings. Wiping it off doesn’t seem to help; chemical trails on cleaned boulders changed the rock surface’s pH balance, which could affect the ability of plants to grow there in the future.
That matters because some climbing spots, such as erratic boulders (the study’s focus), host unique ecosystems. These erratic boulders—rocks scattered across the globe by glaciers at the end of the Ice Age—are islands of vegetation, different from the land they sit on. As such, they may hold information about that era and how these plants travel.
...while colored chalk can help mitigate visual blight, it doesn’t prevent environmental damage. Most colored chalks contain magnesium carbonate along with other ingredients"