“London is open”. So proclaims Sadiq Khan, along with like-minded celebrities, on his London Mayoral Office YouTube channel, and embedded in a page on the City Hall website. “I am incredibly proud to be Mayor of a city that is so comfortable in its diversity, proud of its history…”
A press release this summer, however, suggests the Mayor underwent a change of heart: “Our capital’s diversity is our greatest strength, yet our statues, road names and public spaces reflect a bygone era…”.
Despite the mysterious disappearance of pride in London’s history, his piety towards diversity has endured. Indeed, he plans to “improve [sic] diversity in the public realm”, assuming it is of undeniable benefit. Well it could be so. But before we can interrogate such a claim, we must agree on what exactly ‘diversity’ is, and how to measure it. The champions of diversity however, despite being numerous and powerful, seldom offer methods for its quantification.
Fortunately, biologists have long been interested in another form of diversity – biodiversity – and have developed answers to this question. Robert Whittaker, an influential American ecologist, theorised that diversity can be measured on (at least) two levels.
The first, alpha diversity, evaluates the abundance of species within a local site: a tree accommodating several kinds of species has high alpha diversity. The second, beta diversity, reflects the diversity between sites. Picture a group of trees. If each tree harbours the same combination of species, the group has low beta diversity. Conversely, if they contained different species between them, the group has high beta diversity. Important to note is that while diversity can be measured in these two ways, high alpha is not always accompanied with high beta.
These measures of diversity can be applied outside of biology. Papua New Guinea, home to around 9 million people, boasts an extraordinary 832 living languages. Having arrived in the region over 40,000 years ago, the various Papuan tribes have been isolated for millennia due to the country’s dramatic topology, including mountains, swamps and rainforests. Such isolation induced the linguistic (and cultural) diversity of the nation, a characteristic of which it is deeply proud.
Villages are accorded their own courts, with their own jurisdictions derived from traditional tribal customs. Each village is therefore culturally and linguistically homogenous: low alpha diversity. The heterogeneity between villages however – the beta diversity of Papuan regions – is exceptionally high. If the tribes of Papua New Guinea were mixed, it would increase the alpha diversity of each village. This would however also entail a decrease in beta diversity: villages with similar cultural cocktails, no longer distinct from one another. And in the long term, with the need for communication and without the preserving effect of isolation, the unique languages and cultures of each group would – at least partially – melt into each other, eventually decreasing alpha diversity.
This process is not simply theoretical: history is littered with examples. The peoples of France, prior to her famous revolution, were a collection of fragmented and isolated regions, each with their own customs and habits . Not only was there immense diversity in accent and dialect, but also in distinct languages: Occitan, Breton and Franco-Provençal to name a few. In pursuit of national unity, the Revolutionary and Napoleonic armies forced the mixing of people between regions while privileging the French language alone, ultimately leading to a dramatic crash in linguistic diversity†. And language, being the principal expression of culture, became the vessel through which French cultural homogeneity was reinforced‡.
The mixing of peoples, therefore, resulted in a decrease in diversity. Therein lies the philosophical irony at the heart of the European Union, reflected in its motto: “In varietate concordia” (united in diversity). The centralisation of law and unrestricted movement of people are seen as antidotes to the poison of nationhood. The Union’s most fervent supporters dream of the total dissolution of borders: a European empire§, sharing and celebrating all cultures in the great brotherhood of Man. But though alpha diversity will increase temporarily, the accelerated mixture of people and culture would make Europe more homogenous. In other words, beta diversity would plummet.
Those who truly appreciate diversity should be hesitant about mass movements of people – and globalisation in general – as its continuation could diminish what makes mankind truly beautiful and diverse. Despite the Mayor’s assertions, nowhere is made special by being a generalised, superficial mélange of the world’s cultures: to be characterised by everything is to be characterised by nothing. If all cities were such a mix, would any of them be remarkable?
Rather, the specific differences between places are what make each place interesting. We are charmed by the peculiarities which typify a local culture, organically emerged through centuries of tinkering. It is what makes Italy so gorgeously Italian; what makes Greece so wonderfully Greek; what makes Japan so splendidly Japanese. And the diverse tribes of the amazing Papuan islands would agree that a deliberate mixing up of villages, far from an enhancement, would instead be the devastation of diversity.
† The mass movement of people need not be engineered from above to produce the same effect. The industrialisation of Britain led an exodus from rural to urban centres, prompting a decline in the diversity of local dialects, which collapsed into more generalised regional accents. This phenomenon, termed ‘dialect levelling’, has accompanied movements of people throughout the world.
‡ Indeed, linguistic diversity is among the best proxies to measure cultural diversity across the world: if the former declines, so does the latter 
- Many empires and imperial powers deliberately encouraged or enforced geographic displacement of their subjects, while privileging their lingua franca. Through necessity of communication, languages – and thereby cultures – disappeared.
- Forrest AI, Jones P. Reshaping France: Town, Country, and Region During the French Revolution. Manchester University Press; 1991.
- Fearon JD. Ethnic and cultural diversity by country. Journal of economic growth. 2003 Jun 1;8(2):195- 222.