The global climate and biodiversity crisis necessitates both infrastructural changes and widespread behavioral shifts. Studies consistently demonstrate that ecovillagers exhibit significantly lower carbon footprints than the average population. For instance, research in Italy, Germany, Romania, and Spain reveals a 16% lower carbon footprint among members of green grassroots initiatives, while a Danish study shows a 28% reduction among members of green communities compared to the national average. This reduction is distributed across various consumption categories, with particularly significant decreases in energy (38%), transport (27%), and food (44%). A Danish ecovillage even shows a remarkable 60% reduction. This lower footprint stems from several factors: a strong collective identity and focus on sustainability fostering mutual support and lifestyle changes; specialized knowledge exchange through informal interactions; sustainable physical and social infrastructure; and a lifestyle often characterized by part-time employment, reduced consumption, self-sufficiency, and debt-free living. However, the traditional ecovillage model faces challenges in scalability due to its slow, costly, and exclusive nature.

Existing literature extensively documents the positive environmental impact of collective action within green communities, highlighting significantly lower carbon footprints compared to national averages. However, studies analyzing the diffusion and spread of these models remain scarce. Classical diffusionism, drawing parallels between cultural traits and adaptable organisms, and neo-diffusionism, emphasizing cultural appropriation, fall short of explaining the uneven spread of ecovillages and the rapid rise of green neighbourhoods. Rhizome theory, while acknowledging the decentralized and non-linear nature of community formation, fails to account for the sudden surge in green neighbourhoods. Tipping Points Theory, however, offers a more suitable framework by suggesting that a critical mass of factors—media coverage of the climate crisis, accumulated experience, and a sufficient number of committed individuals—might explain the rapid proliferation of green neighbourhoods.

This paper draws primarily on qualitative data gathered through extended participant observation. The first author, with extensive experience living in and facilitating the creation of eco-communities and involvement in relevant organizations, provides insights into eco-communities. The second author, a researcher closely involved in the green neighbourhood movement, offers perspectives on this avenue. Both authors are members of the SAMSKAB research project, which investigates the establishment and social-environmental impact of green communities in Denmark. The data are based on first-hand knowledge and personal experience, encompassing micro-level observations (daily life), meso-level interactions (municipality engagement), and macro-level considerations (national legislation and international collaboration).

Denmark's eco-housing movement, originating in the 1970s, evolved to include ecovillages in the 1990s. While approximately 35 ecovillages exist (mostly rural), few have been established recently. However, a significant shift involves the emergence of eco-communities, with about 25 created in the last eight years. These communities often arise through top-down municipal support or from the side through professional developers. Bottom-up ecovillage development proves challenging, demanding significant time (5-10 years) and expertise to navigate legal, financial, and building complexities. Municipalities actively promote eco-communities to attract skilled residents, offering land, flexible planning, and administrative support. The rise of professional eco-community builders further facilitates this process, providing turnkey solutions and community-building expertise. The increased number of eco-communities in recent years demonstrates this approach's effectiveness. In contrast to ecovillages, eco-communities often reside in suburban areas, exhibiting a more pragmatic approach to sustainability. While ecovillages and eco-communities coexist and often share resources (community builders from ecovillages help facilitate eco-communities), the latter represent a faster, more mainstream model. A second major trend is the proliferation of green neighbourhoods, which rapidly expanded across Denmark since 2019. These are informal groups of neighbours collaborating on various sustainable activities, from communal meals to energy communities. Their decentralized, non-bureaucratic organization contrasts with formal associations. Although lacking the deep carbon footprint reductions of ecovillages, green neighbourhoods demonstrate remarkable inclusivity and broad participation, offering a potentially significant impact due to their widespread reach.

The findings highlight the successful adaptation and expansion of ecovillage principles into more accessible models. Eco-communities and green neighbourhoods, while potentially yielding less dramatic individual carbon footprint reductions, demonstrate considerable success in reaching a larger population, suggesting a broader environmental impact through scale. The contrasting organizational structures—the formal, structured approach of ecovillages versus the more fluid, community-based approach of green neighbourhoods—reflect different strategies for achieving sustainability goals. The comparison highlights how the inherent qualities of ecovillages (strong community, deep commitment, shared resources) can inspire similar yet more accessible practices that may potentially accelerate the pace of widespread sustainable practices. While these models demonstrate different levels of commitment and impact, the overall success in spreading the core principles of ecovillages to a wider population showcases the potential for larger-scale environmental transformation.

Ecovillages, despite their significant positive environmental impact, are limited in their capacity for widespread adoption. Their evolution into eco-communities and the spontaneous emergence of green neighbourhoods demonstrate a successful strategy for disseminating sustainable practices more broadly. The rapid growth of these alternative models suggests a significant shift in societal attitudes towards sustainability and collective action. Future research should focus on quantitatively measuring the cumulative environmental impact of these initiatives and exploring strategies for further enhancing their effectiveness and inclusivity.

The qualitative nature of the data limits the generalizability of findings. The study primarily focuses on the Danish context, limiting its applicability to other cultural and societal settings. The rapid growth of green neighbourhoods means that long-term data on their sustainability impact are currently unavailable.