Are you suggesting that white people who live in cities don't lack access to nature? Or just that it doesn't matter?
The main reasons that in the UK more ethnic minorities live in cities is the same reasons because that pattern follows through in almost all countries. Relative newcomers tend to settle in cities for a few reasons. This has been the case for centuries and typically has to do with trade and how people move. Peasants, the people on the land, are typically not newcomers.
The other, more recent element is that rural areas in developed countries have been losing population to cities for decades.The same forces that keep rural residents moving to cities tend to keep most people from moving to the country - there are few jobs there. Economic activity is mainly found in cities. And it can be hard for incomers in small rural communities socially too.
This is true in places like Asia and Africa too, except it's not the same people who are ethnic minorities. But if you go look at, say, European, or Jewish, or Asian newcomers in west Africa, you tend to find them in towns and cities, rather than rurally.
None of that is about racism, it's about how populations disperse.