Biodiversity is currently experiencing a massive crisis, one just as serious as that facing the climate. Both are waiting on badly-needed solutions. Over 10 percent of the species native to Europe are threatened with extinction. Operators of existing solar parks as well as project developers can counteract this crisis to some extent in their planning phases by designing their solar parks in an environmentally-compatible manner. Guidelines from the Bingen Technical University of Applied Sciences offer concrete, practical advice for how to approach this problem. More and more project developers are also signing on to the “Good Planning” voluntary commitment, which includes provisions for supporting biodiversity. In this article you will learn how to increase biodiversity in existing solar parks.

How biodiverse are solar parks?

In most cases, solar parks do benefit biodiversity. They can provide helpful “stepping stones” for rare flora and fauna in an agricultural environment. This has been shown by studies from the German Association of Energy Market Innovators as well as by accompanying studies from TH Bingen. The practical guidelines for nature-compatible, biodiversity-promoting solar parks have been derived from these studies. The decisive factor for how much of an increase can be made to biodiversity is always how the area was previously utilised. Particularly for fields that have previously been intensively cultivated, this increase is high.

As to risks to biodiversity posed by open solar installations, the German Federal Agency for Nature Conservation lists the following impacts:

• Interference with and alteration to the natural soil profile
• Compaction of soil areas due to vehicle movement and storage of construction materials
• Impairment, alteration, and destruction of habitats for existing species (flora, fauna) as well as interruption of migration paths
• Alteration of the water regime and soil-water balance caused by module superstructures

The authors of the Bingen study demand that more be done for biodiversity than solely the benefits arising passively from solar parks. They distinguish between obligatory conservation mandates, such as impact regulation and compensation and species protection requirements, and voluntary commitments that go beyond these measures. According to their argument, added value for the natural environment can only arise with additional measures.

During planning, value for biodiversity can be created, among other things, by maintaining larger row distances (> 3.5 m, at best 5 m), sealing as little land as possible, placing fences 15 to 20 cm above the ground, keeping migration corridors for large animals open in cases of large installations (from approx. 500 m), or leaving space for flowers or hedges.

But what exactly can operators do?

Have a concept for conservation created

Conservation and care adapted to the site and ecologically oriented is decisive for the natural compatibility of an area. Specialised planners can also develop so-called “target biotopes” for existing plants and derive differentiated conservation management from them. You can learn what should be sown or planted, how the land should be kept ecologically open, whether topsoil should be built up or the soil hauled away, and much more.

Of course, there is greater opportunity for this when planning a PV plant. Local natural conservation can also be involved in this process. Highly exemplary solar parks could even play a role in public relations with sponsorships (e.g. via conservation and environmentalist associations).

Maintaining areas: mowing or grazing?

The land must always be kept clear to prevent shadows from growing over the PV modules, reducing yield. In order for this land to grow into a species-rich grassland, different forms of extensive cultivation or maintenance can be adapted to the site and the PV plant. This means first and foremost that neither poisons nor fertilisers are used.

If the area is to be mowed, mowing technique plays a role: TH Bingen recommends sickle bar mowers with a minimum height of 10 cm. When mowing should occur and how frequently (or ideally, infrequently) can also be determined from a conservationist point of view, taking into account the operator’s needs. Unfortunately, with PV modules installed close to the ground, mowing must be done more often. If a previously fertilised field is to be harvested, the mown cuttings will need to be removed. Mowing can also be organised in an alternating pattern, leaving suitable portions of the land unmowed each year to offer forage, habitat, and refuges in winter.

Even better for biodiversity is grazing using sheep or goats. Successive grazing ensures that flora is always present in sufficient numbers. The animals’ claws also open up the soil, where less-competing species can germinate, or wild bees can settle in. It is important for grazing that there are no flat bars protruding from the modules and that sharp edges are removed and free-hanging cables avoided. Likewise, the inverters and plugs should be protected, as animals like to rub against them. The minimum height of the lower edge of the solar modules should usually be 80 cm (as is already the case with many installations), so that sheep can walk underneath and do not become restless being separated from each other.

Creating a biotope

The seed or planting material should be as native to the area as is possible. For a cost-effective method, the seeds can also be introduced via hay coming from neighbouring grassland. Depending on the location, additional biotopes can also be created:

• Dry biotopes such as sand, rubblestone, or dead wood piles.
• Wetland biotopes such as ponds and pools at the edges of a solar plant. These can be fed by rainwater running off from the module structures.
• Nesting supports for birds, bats, and wild bees.

Click here for the guide to nature-compatible and biodiversity-friendly solar parks from TH Bingen (in German).

“Good planning” commitment

The german solar industry has recognised the opportunity to make a contribution to biodiversity, as well as environmental protection. Ever more photovoltaic enterprises are signing the voluntary commitment from the Association of Energy Market Innovators (BNE). Learn more about the voluntary commitment for good planning of ground-mounted photovoltaic systems here on the blog. As well as increasing biodiversity, the voluntary commitment includes obligations to communities, administrations, citizens, fair business with farmers, and the integration of photovoltaic systems into the landscape.

What does biodiversity mean for investors?

For investors with a focus on impact, PV projects that have proven added value for biodiversity can be particularly attractive. The ecological benefits can be well-demonstrated with photos and facts.

While some environmental benefits are achieved while saving on costs, others require more space. To some extent, this comes at the expense of yields or increased leasing and maintenance costs. Investing in a specialist planner at the start of a project is helpful. Potential compensation can be organised so that it is provided directly on-site. Moreover, the question is one of prioritisation. In addition to financial return, the demonstrable ecological return can be perceived as attractive. Biodiversity, but also additional biotopes and the involvement of natural conservation can also increase the acceptance of PV projects by locals.