The consumption of land by construction leads to a loss of soil functions with permanently negative effects on the efficacy of the natural balance. Soils have a large variety of functions which need to be protected: they provide habitats for plants and animals, they store and filter the groundwater, they act as buffers against pollutants, they are the foundation for agriculture and for healthy living, and they are an archive of natural and cultural history. These fundamental functions of the soil must be secured by adequately taking the needs of soil protection into account when planning for the future.
Soil is increasingly gaining importance in societal and ecopolitical matters, especially in view of its adaptation triggered by climate change, the carbon storage capacity of the soil and biodiversity. As a result, national measures and regulations have been implemented to reduce new land consumption and impervious soil coverage, and to provide sustainable land management in cities and municipalities.
In 2002, the Federal Government already formulated the goal of reducing new land consumption to 30 ha per day by 2020 (BMUV 2021). This goal was not met, however.
With the German Sustainable Development Strategy 2016, the Federal Government postponed the 2020 goal of 30 hectares to “under 30 hectares per day” by the year 2030 (indicator of sustainability target 11.1a, Federal Statistical Office 2018). In the updated Federal Government’s Sustainable Development Strategy 2021, the aim is to establish a closed-loop land-use regime by 2050, meaning that, in net terms, no additional land shall be developed for the purposes of settlement or transport (Federal Government (ed.) 2020; Federal Statistical Office (Destatis) (ed.) 2021a).
“Germany’s mean, measured across the four years between 2017 and 2020, indicates that the settlement and traffic area increased by an average of about 54 hectares per day. The indicator has thus slightly risen compared to that of the preceding years (52 hectares per day between 2016 and 2019).” (translated from Federal Statistical Office (Destatis) (ed.) 2021a, 2021b, 2022). Sustainable Development Goal 15 addresses the protection and the sustainable use of the resource soil and indicates degradation neutrality by 2050 as its top priority. Impervious soil coverage (“sealing”) is one of the 16 core indicators by which sustainable development in the State of Berlin is measured (Amt für Statistik Berlin-Brandenburg 2021). With these activities, a process was initiated in the State of Berlin with the aim of sustainably addressing the inclusion of the limited resource of soil in building and planning processes based on legally anchored regulatory options.
The goal of the Senate Department for the the Environment, Urban Mobility, Consumer Protection and Climate Action and the Senate Department for Urban Development, Building and Housing is therefore to provide instruments for an active, practice-oriented land management system. These make it easier, in particular, for the soil protection authorities to perform their tasks as public authorities, e.g. in the context of urban development planning, and of competently integrating aspects of soil-protection in the environmental impact assessment process.
One problem that appears regularly in planning practice is that the impervious covers required for developing an area can hardly be offset in material terms. In principle, the best compensation would involve the removal of the impervious cover (de-sealing) of another area. However, due to the restrictions of availability of most land for such measures, it is difficult to find areas in Berlin where the impervious cover may actually be removed. It is then not possible, using the Environmental Impact Assessment, to implement such measures, due to the lack of any adequate available land. Proposals for the removal of impervious coverage usually have a chance to be realised if areas with the potential of having their impervious cover removed are already known, have been checked for suitability, and are listed in the register.
An initial step was the compilation of Environmental Atlas Map “Planning Advice for Soil Protection”, an important planning instrument for soil protection assessment. The weighing of the various functions and sensitivities of the Berlin soils permitted a differentiated evaluation of urban development planning. For example, in the case of soils which, from a soil protection viewpoint, were classed as particularly valuable, the search for alternative sites for relevant development planning projects was recommended.
The project “Potential for the Removal of Impervious Coverage in Berlin” (only available in German) was initiated to improve the availability of areas for impervious coverage removal as a second step. The goal of the project is to identify and evaluate land which could potentially have its impervious cover permanently removed in the foreseeable future. To the extent possible, the efficacy of the soil is to be restored, and habitats valuable from a conservationist point of view are to be developed for plants and animals. In addition, the aim is to support a geographical decoupling of the sites of impairment and those of restoration by means of a city-wide survey and a uniform system for the evaluation of the recorded areas. In individual cases, the instrument of impact mitigation regulation (according to construction law and conservation law) may be considered an option here. The recorded areas generally represent available land that may be used to offset human intervention in the soil or the permanent loss of soil functions. They also indicate land suitable for impervious coverage removal measures within the framework of funding measures.
In the context of the project phases since 2010, a survey was carried out in all Berlin boroughs, all four Berlin forestry agencies, and among private owners. The most recent update was carried out between January 2022 and December 2022. The data obtained during this survey process was compiled in a centrally managed database, into which further information and suggestions for areas may be continuously entered by the various actors in the public administration also in the future.
Moreover, private landowners are to be able to not only obtain information on potential areas for the removal of impervious coverage, but also, if they wish, to propose their own areas which are unsuitable for construction purposes and which, after an examination of their suitability, may be added to the portfolio.
In order to continue to support the implementation of removal measures, a tool to derive simplified cost approaches for the expected dismantling costs has been prepared (an Excel input file simplifies the cost estimate for an impervious coverage removal measure). Based on the review of the literature, proposals for a guide to action have been developed. They address technical and qualitative standards for the regeneration of soil functions following the process of removing impervious covers (all documents only available in German). In 2021, a report on successful removal measures was published, outlining the project process, financing and the involvement of the Spandau borough office (SenUVK 2021).