- Biodiversity in brownfields - 09/08/2021
Moving from Dublin City to rural Ireland as a child was a bit of a shock to my system. Up to that moment I had grown up surrounded by pavement and tall dull buildings as far as the eye could see, however, now I lived in a house surrounded by fields upon fields of cattle and crops. I thought I lived in an area surrounded by nature, but it wasn’t until I got older that I realised the endless stretches of fields around me all contained the same few species.
Credit cover picture: Dissonancefalling is licensed under CC BY-NC-SA 2.0
As a child, I gave little thought to this homogeneity. The one thing around me that did catch my attention was the large deserted building site at the back of my house. Like many, we moved into a brand new housing estate during the Celtic Tiger, only for the inevitable bust that occurred shortly after we moved in to halt the construction on the rest of the estate. As children, we were always warned to stay away from the empty site. Filled with abandoned equipment and precarious structures, the place was a death trap. For years, despite the odd bonfire on Halloween, the site remained virtually untouched. Forever to be labelled an eyesore. A waste of land.
That was until I went to university to study Zoology and took a module in Restoration Ecology. During this time, I learned that Mother Nature may not have been as idle over the many years that construction companies have been. The term brownfield site came up on my radar and I realised that maybe that eyesore at the back of my estate might hold more value than I previously believed.
What are brownfield sites?
Brownfield sites have been defined as “land that was previously developed for housing or industry but has since been abandoned and recolonised by different ecological assemblages” [1]. While these sites are typically described as “dangerous” or “eyesores” and can have negative connotations to them, research has shown that these brownfields are highly important for biodiversity as they are capable of harbouring rich and sophisticated ecosystems capable of supporting rare and threatened species.
While governments are starting to acknowledge the importance of brownfields and the role they play in protecting biodiversity, such as the UK government adding some brownfield sites to its list of priority sites listed in its Natural Environment and Rural Communities Act 2006 (NERC Act), many of these sites still face threats of development [2].
There are many types of brownfield sites, with the two most important broad categories being described as wetland or dry ground. Wetland brownfields are important as they provide refuge for waterbirds, whose natural habitat availability has been shrinking. Dry ground sites, are typically well-drained, poor in nutrients and sometimes contaminated and have been described by conservationists as highly important for providing havens for rare or endangered species [3].
Why are brownfields important for rural Ireland?
The expansion and intensification of agricultural practices have been closely linked to the depletion of biodiversity. It has been suggested that as much as 23% of species diversity once associated with European farmland has been lost during the period 1970 and 2000 [4]. It has become clear that biodiversity plays a fundamental role in sustainable agricultural systems. It has also been determined that increasing habitat heterogeneity in the rural landscape would play an important role in reversing the decline in farmland bird species. So if it has been agreed that more diverse landscapes in rural Ireland would benefit biodiversity and in turn would have a positive impact on agriculture, perhaps it would be beneficial to not only focus on increasing biodiversity on agricultural land but also factor in the importance of brownfield sites that have become widespread across Ireland since the 2010s when a surge in ghost estates, and in turn abandoned building sites, was seen in rural areas.
Of course, it’s important to stress the importance of protecting and promoting biodiversity on agricultural land, but maybe we shouldn’t ignore the potential biodiversity goldmines that we have potentially been casting scornful looks at for the past decade.
The brownfield site next door
At the beginning of the summer, I contacted Dr Marcus Collier and the Connecting Nature project about summer research opportunities and we got on the topic of the abandoned building site in my estate. We concluded that I had the opportunity to conduct research right on my doorstep. Once we worked through the logistics of the site location we came up with a plan. The plan for the research was to create a habitat map of the site, conduct botanical, invertebrate pollinator and bird surveys, and compare this to similar surveys conducted in a neighbouring agricultural field. This research aimed to bring attention to brownfield sites and to show that they can play an important role in conjunction with sustainable agricultural practices to increase the heterogeneity of the Irish rural landscape to protect and promote biodiversity.
ArcMap 10.7.1 was used to create the habitat map and habitats were classified according to Fossitt (2000) – A Guide to Habitats in Ireland. Once the map was completed, I decided that to get a complete picture of the brownfield site and the potential species it was home to, botanical surveys of multiple habitat types were required. Botanical surveys of grassland (GS2), hedgerows (WL1) and recolonising bare ground (ED3) were conducted. Transect sampling methods were used to record invertebrate and bird species. The same methods were used to study an improved agricultural grassland (GA1) directly beside the brownfield.
So on a few sunny days in June 2021, I went out into the field with a homemade quadrat, a camera, and a pen and paper to conduct this research.
What was found?
The results of the botanical surveys for each habitat type within the site were interesting because there was minimal overlapping in species types recorded in each habitat.
Each habitat type had a distinct set of botanical species that weren’t found in the others. The recolonising bare ground was recorded to have the highest number of plant species. A survey of a neighbouring agricultural site showed very little diversity in plant species, with perennial ryegrass dominating the majority of the site. Several grass species were recorded in the brownfield site, including Yorkshire fog (H. lanatus) and sweet grass (H. odorata).
The invertebrate pollinator survey also indicated the high biodiversity of the site, in which a range of bees, butterflies, and moths was recorded. Bees were the highest recorded species including the common carder (B. pascuorum), buff-tailed bumblebee (B. terrestris), and garden bumblebee (B. hortorum). Common blue (P. icarus), large white (P. brassicae), and small tortoiseshell (A. urticae) were the butterfly species identified. One micromoth species, Ancylis badiana, was also recorded. The bird species that were identified included Rooks, Wood pigeons, Starlings, Robins, and Magpies.
What does it mean?
This field research is important because it could increase community awareness of how important the areas in towns and villages that are deemed to be “eyesores” could unknowingly be. It’s also important because it could be an indicator that brownfield sites could benefit the goal to increase biodiversity in the rural landscape by acting as a mosaic of different habitat types within one site located between large areas of agricultural land. While the main goal would remain to focus on protecting and promoting biodiversity on agricultural land as it makes up the majority of land use in Ireland (roughly 70%), brownfield sites could supplement the actions undertaken. Brownfield sites could benefit rare and endangered species by acting as a refuge when their natural habitats are becoming fewer and further between.
I believe that the potential benefit that brownfield sites could have to protect and promote biodiversity throughout Ireland should be given real consideration. While the land type could be deemed unorthodox, we live in a world that is changing every day and we must keep creating new ways and be open-minded to adapting to this change.
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