Globalization as Humanitarian Challenge 3:'Everyone has the right to a nationality' (Universal Declaration of Human Rights, article 15)
Statelessness happens when nations dissolve into subsequent national units, as happened after the breakdown of the Sowjet Union or the Republic of Yugoslavia. Until today most documented stateless persons live in Latvia. There are two UN-conventions related to Statelessness. However the bureau was criticized for ineffectiveness before significantly upscaling activities in recent years.  Interventions of the UNHCR since then have avoided statelessness in a number of cases, of Tamils after the Civil War in Sri Lanka and of Slovaks after the separation of the former Republic of Czechoslowakia. The Rohingyas in Myanmar are internally displaced stateless without being granted equal citizen's rights. Myanmar has a highly discriminatory citizen law (1982) but there seems to be also a lack of implementation and documentation.  The UN estimated 810.000 stateless people in 2015. South-East Asian Nations and India did not sign the conventions. It seems to be obvious that areas in which the problem is most pressing are not able to fulfil the 'humanistic' targets envisioned in the declaration.
Some situations are not foreseen and need solutions after negotiations between states, which may be cumbersome. Children of Syrian refugees born abroad are considered stateless, if their father is not documented. The problem is hidden while they are stuck in refugee camps or temporary asylum. But if these people's permits phase out, it will be difficult for them to return, because they have no paper to proof citizenship in their country of origin. Other people feel like nations without a state, the Kurds being a well-known example of pressing concern.
At a time when the nation as the basic unit of the global governance system is increasingly under debate, documented national citizenship is likely to constitute one of the most valuable, and for individual citizens most urgently appreciated, affiliations. National passports less poof then produce citizenship identity. And migration is likely to sharpen our understanding of that appreciation much.
That reminds one very much of the motifs, that once put the system in place. Global migration and trade from the mid 19thcentury on once triggered the debate how the intensifying streams of exchange (of goods, of humans) could be managed. Zones of free markets and liberal values were perceived as meant to be protected against local and / or alien powers, judged as units that at first had to catch up with "civilization".  The introduction of the passport as a document to proof individual identities emerged and was promoted by what we could today call a 'club' of first movers (United States, United Kingdom, Germany). A global process of standardization was initiated to efficiently proof individual identities that were formerly testified by local communities, the working environment or religious bodies. Since then the passport information defines us by our biometrics while keeping shtum about sociometric specifics.
The trajectory of the 'club' draw others into conforming to the system and a process of harmonization and mutual recognition produced over decades an international system of individual identity documentation that today is used at airports worldwide; a system that we are aware of only when it accidentally fails . There were initiatives to establish an international, even global passport as a document, testifying individual global identity. But whereas global citizenship is a buzz word and as well a buzz concept of the current debate about global governance, these initiatives are mostly symbolic campaigns. 
Research in the field of global identity construction will be considerably enriched and done more conscious if historic lines are put into the picture. Converging and diverging interests become visible that produced the 'gestalt' of nation states back then, while defining a frame for citizens identities that, in all variation, is prevalent until today.
Supposed that we are living in a similar time of emergence, giving shape to new standards and procedures, likely again by 'clubs' of first moving actors - and not sure these actors will only be composed of states - it may be wise to re-read one of the most lucid and fare-sighted takes on these issues by Hannah Arendt. In her seminal analysis on "The Origins of Totalitarism" a chapter on "The nation of minorities and the people of the stateless" at first seems to be a mere by-product of the general line of argument. But isn't it addressing possible research questions that the inherent exclusionary character of the Westphalian nation state produces those aliens within and without at the same time?
It is a blunt lesson of history that the 'minority nations' in 1920s Europe finally were not in close solidarity towards each other but decided to feel closest to their respective majority nation state. German minorities abroad in a decisive moment voted against their Jewish minority comrades who protested their treatment in the German 'Reich'.  Arendt called this the 'capture of the state by the nation'. Already the definition of 'statelessness' is telling for her. The 'pure' form of statelessness, expressed in the French term 'de nationalité indetérminée', was acknowledged easily. But what about 'displaced persons', the 'homeless'? People started to seek refuge in a neutral status of statelessness because they feared deportation back into a homeland that turned to be a nightmare.
Re-reading Arendt, one can ask, whether today's practice puts people en masse into a limbo that avoids the label of statelessness in favour of the refugee identity, because this, while certainly provoking public unease, still is challenging the system of nationally defined identities less.
 The UNHCR launched a global campaign on 4 November 2014 to end statelessness within 10 years. For un upscaling of resources to the bureau of Statelessness, see UN document 'Update on statelessness'. Convention relating to the Status of Stateless Persons 1954
Convention on the Reduction of Statelessness 1961.
 Nyi Nyi Kyaw, 'Unpacking the Presumed Statelessness of Rohingyas', Journal of Immigrant & Refugee Studies 15 (3), 2017.
 Fundamental anaylsis, also of blind spots of research centered (only) on transatlantic migration flows: AdamMcKeown, Melancholy Order: Asian Migration and the Globalization of Borders, New York 2011.
 'Major airport delays in Australia and New Zealand as global passport system goes down',The Guardian, 22 May 2017.
(*) The World Passport is a fantasy travel document sold by the World Service Authority, a non-profit organization founded by Garry Davis in 1954, therefore in the year of the first UN 'Convention relating to the Status of Stateless Persons'. The 'Amherst Declaration on Global Citizenship' of The Global Citizens' Initiative (TGCI) is an example of a civil society initiative heading in this direction.
 Hannah Arendt, The Origins of Totalitarism, 1951 (German 1955), especially ch. II, 9 'Decline of the Nation State'. Arendt refers to The Congress of European Nationalities founded 1925 (dissolved 1938), a non-governmental body founded by representatives of national minorities.