The ecological effects of red wood ants of the Formica rufa group extend over several trophic levels. Due to their multiple roles in the environment they can be referred to both as keystone species and ecosystem engineers. Therefore any change to their status and distribution affects not only the ants themselves but a more widespread suite of species (including myrmecophiles and myrmecochorous plants) and ecosystem processes such as nutrient cycling (see Chapters 6, 7, 8 and 9).

Where they occur, wood ants are usually populous and, as such, they need abundant and stable resources and favourable abiotic conditions for reproduction. However, while the workers are numerous, only queens and males reproduce, which is why effective population sizes and thereby conservation needs are easily underestimated. In addition, it is large colony size which makes the wood ants vulnerable, because they need relatively large habitat patches with stable food sources to maintain viable colony functions. Therefore, loss of suitable breeding habitat is a major threat and many of the red wood ants have a status as ‘near threatened species’ globally (see Table 1.1 in Chapter 1). However, habitat loss is far from the sole threat since pollution, climate change and natural causes of decline (e.g. pathogens) also have an effect on red wood ants.

The threats against wood ants can be categorised as: (1) harmful changes in availability or quality of food (e.g. loss of aphids, contamination of food); (2) loss of suitable habitat (e.g. increase of agricultural and urban areas); (3) changes in climatic conditions (e.g. climate change, microclimate change); (4) natural causes of decline; and (5) their interactions. These threats, and how they can be addressed, are the subject of this chapter.

Habitat management

Wood ants are mainly forest-dwelling animals. Their large colonies are dependent on vast aphid populations living in tree canopies. Therefore, the most extreme events affecting wood ants are in relation to forest management, which has also been the focus of much of the published literature. Severe forest management practices such as clear felling, or felling with some retention trees, clearly cause negative biotic and abiotic changes in the environment, and for wood ants this means changing the availability of aphid-originated food and microclimate (Figure 12.1).