Significant changes to habitats and vegetation structures occurred from 2006 onwards as a result of the implementation of the "Ecological Wall Renovation" project funded by the German Federal Environmental Foundation (DBU) and the subsequent extension of the construction project to all citadel walls from 2017 onwards.

Tree felling accompanying the project and, not least, the spread of sooty bark disease among maple trees have led to a significant reduction in the valuable natural forest-like areas on the citadel. 

In order to ensure ecological functions as quickly as possible, it was also necessary to update the maintenance and development plan for the citadel. This plan regulates in detail the maintenance of vegetation in the protected landscape component "green space of the citadel with moat area" and the adjacent areas. It also shows the new and expanded path system of the citadel as a connection between Mainz's old town and the upper town. 

The plan also formulates measures for the development of valuable biotopes, e.g., for light-dependent plant species and heat-dependent animal species. It thus serves the needs of both humans and nature in equal measure.

• Measures such as the development of flower-rich borders in sunny areas at the foot of walls, shade-loving herbs and grasses at the edge of woodlands, the planting of new shrubs and trees, and ivy plantings
• creating meadows in sunnier areas, and protecting red list species such as powdery mullein (Verbascum pulverulentum), lizard orchid (Himantoglossum hircinium L.), and dwarf bird's-foot trefoil (Medicago minima) are also part of this.
• The maintenance and promotion of connectivity, the creation of replacement habitats for wall-dwelling animal species, such as the use of habitat stones in walls, the construction of dry stone walls as replacement habitats for insects and sand lizards, and the creation of entry holes for bats are all part of the maintenance and development plan.