While a transnational sociology of the professions has opened up, the question of how to conceptualize the trans-local arenas in which contemporary professional projects compete for expert jurisdiction, organizational change, and wider policy reform remains elusive. Three literatures, in particular, have made important contributions: neo-institutional approaches to the re-scaling of professional organizational fields; Bourdieusian approaches to inter-and transnational fields of expert power; and approaches deploying Andrew Abbott\'s notion of linked ecologies in analyzing transnational expert politics. In reviewing these debates, this article makes the case that Abbott\'s core topological notion of \'ecology\'-understood as differentiated and competitive arenas for professional claims-and alliance- making-has certain advantages when it comes to re-scaling and specifying the trans-local character of many contemporary professional projects. In particular, the article argues, this notion allows the analyst to view issues of spatialization and scale-making, and hence the making, linking, and boundary-drawing of specific expert jurisdictions, as themselves major issues of negotiation and struggle for contemporary professional groups. This conceptual and methodological argument is fleshed out in the article in relation to an on-going comparative research project on how professional groups in Denmark compete and cooperate for local organizational change in relation to border-transcending challenges of climate adaptation, lifestyle-related diseases, and economic innovation. By mapping the three case histories in terms of their patterns of local-transnational relations, the article ends by specifying some of the methodological challenges for a qualitative and comparative study aiming to capture emerging and variable modalities of trans-local professional projects.