This article is part of a thought leadership series we’re producing in tandem with the Convention on Biological Diversity (CBD) 15th Conference of the Parties (COP15).

Read the introductory article here.

Introduction

Urban planning plays a crucial role in protecting biodiversity. In this article we look at how development and construction directly affects habitats of native species on site and how developers can mitigate biodiversity loss and even try to strengthen biodiversity. They can do this by increasing green areas, connecting ecological corridors and providing habitats and nesting places for native species in the construction of buildings. But how can a developer prove their new project will deliver on biodiversity targets?

Measuring biodiversity by native species

Biodiversity status is often measured using the relative Mean Species Abundance (MSA) of originally occurring species. This indicator measures the average population of native species (plants and animals) in an ecosystem or area compared to how (we assume) it was before it was disturbed. The reason that biodiversity is measured by looking at native species, is because ecosystems tend to exist by grace of interactions between species that are dependent on each other. A non-native plant, a so-called exotic, often does not fulfil the required functions within that ecosystem at the right time. An exotic may therefore well be of little or no value for biodiversity on site while it does take up nutrients and space. In 2010 the global MSA was valued at approximately 70%. In Europe it was less than 50%, and in the Netherlands it was approximately 15%. There are several reasons for this. One is the decline in native species’ habitats, both in terms of quality and quantity. Especially in areas with such historic decline in species, the ecosystems in the built environment have become as important as those in officially protected Natura 2000 areas.

Quantity of habitat

Urban planners are and will be aiming for better preservation of existing habitats, preventing fragmentation of habitats and compensating for habitats that have to be removed because of construction. The UK Environment Act 2021 is an example of how local authorities can help preserve and enhance biodiversity. The Act introduced a legal requirement for biodiversity net gain (BNG) for new developments. Whilst the provisions are not yet in force, they represent one possible solution to the, at times competing, demands of new development and the need to protect biodiversity. The Act requires developers to carry out a baseline assessment of the biodiversity of the building plot before construction begins. Thereafter, it requires the biodiversity value attributable to the development to exceed pre-development biodiversity value by at least 10%. The increased biodiversity value can come from onsite habitat, offsite biodiversity gain or, as a last resort, biodiversity credits.

Quality of habitat

When we look at quality of habitat, nitrogen is a critical factor. Because of the increase in industrial activities, many (EU) protected green areas that are home to important habitats are affected by high levels of nitrogen emitted due to intensified agriculture, traffic and industry. Nitrogen is released at the site of the activity and is then blown into nearby areas. If too much nitrogen falls on a vulnerable green area, it can have significant negative effects (including soil acidification to such an extent that specific plant species - characteristic of the type of habitat to be protected in the area - can no longer survive). Excessive nitrogen deposits result in long-term deterioration of the existing flora and fauna, which constitutes a violation of the European Habitat Directive.

Authorities must enforce biodiversity preservation

In the past few years, as became evident through regulations and case law, governments have sharpened their aim to prevent the deterioration of (protected) green areas. This is an important reason why an environmental impact assessment (EIA) is mandatory for activities that might have a significant negative environmental effect on a nearby area. In the Netherlands, the decline of biodiversity has reached a critical point, affecting the development of new projects. Through national permit obligations and exemptions, developers have to follow strict assessment frameworks to prevent further decline. In light of their responsibility to promote biodiversity in green areas, authorities can even revoke previously granted permissions for activities if conservation measures are not available or sufficient. This shows how urban planning instruments play a direct and vital role in the preservation and enhancement of biodiversity.