All over Europe self-organised civil society movements are emerging to tackle local challenges, becoming active players in local governance processes. These social experiments have even been intensified as a result of tight public local budgets. Their activities contribute to the functioning and well-being of a European society aiming for sustainability. Preserving the availability of bio-diverse green spaces is crucial for the socio-ecological transition of cities since besides providing recreational opportunities for city dwellers, they yield essential ecological benefits from cleaning the air to reducing noise, but also provide habitat for many species and plants and reduce local vulnerabilities to extreme climate events. In cities in which local governments have severe difficulties in affording the provision of green space, new self-organised initiatives have emerged for maintaining and even developing them. Initiatives such as urban gardening have proven that people are able to cooperate, to organise themselves and to take over responsibility for green spaces as well as even introducing new practices that support the socio-ecological transition.