Globally reptiles, like the adder, have been declining due to threats such as climate change and they have higher extinction rates due to smaller population sizes.

Adders in particular are declining across their ranges in Europe, including the UK. My research focused on the declining Surrey adder population. Surrey has the second largest habitat (by area) to support adders in the UK, after Devon. However, the habitat in Surrey is much more fragmented by urbanisation due to its proximity to London.

The Surrey Amphibian and Reptile Group (SARG) gave me data on adder sightings from 1881 to the present day. From this, I was able to map the distribution of adders across Surrey over time alongside known threats to adder populations such as wildfire heatmaps.

I found that the number of adder sightings declined from pre-1990 to 1999, but increased from 2000 onwards – probably due to improved survey methods. My work also suggests that Surrey’s adders are threatened by major roads (e.g. the M25), urban development, and wildfires which all lead to habitat fragmentation. In response to these findings, I suggested future conservation policies/projects, from improving adder-focused development plans to taking creative public outreach storytelling approaches from adder sightings to increase public awareness.

One policy suggestion should be the creation of wildlife corridors on roads such as the M25, A3 and M3 to allow adders (and other wildlife) to move freely without physical barriers that have a high-risk crossing. A wildlife corridor reconnects once-isolated populations by allowing a passage, such as a bridge or area of land, varying at different scales (Gracanin and Mikac., 2023). These wildlife corridors will help to reduce the formation of isolated populations and lead to higher genetic variability, reducing the chances of inbreeding. For example, artificial underpasses or overpasses along these roads would allow adders to move across and open their habitat range and hopefully help prevent their decline. It is also crucial for adders to be considered during the construction of new major roads and improvement works to reduce the impacts on local adder populations. 

Another policy that this research has highlighted is the need to consider Adders during new housing or urban developments. Adders are shy creatures that will avoid interacting with humans. However, encroachment onto their habitat could result in increased sightings of adders in urban areas, which, combined with a negative public presence, could harm adders or the public. 

A final improvement to current policy/projects tackling public perception of adders could be carried out using the comments from adder sightings to give a story to each data point on the map. To start with, new projects could be carried out in Surrey to test the effect of storytelling adder sightings to improve public perspective, from the positive to the negative, allowing for the dangers of adder surveying to be highlighted but also the need for conservation and how the public can help but protect themselves.

These new conservation policy suggestions are critical to protecting the UK’s only venomous snake.

I am grateful to The Surrey Wildlife Trust and Surrey Amphibian and Reptile Group (SARG), which kindly provided support and the data for this research.

Written by Louise Riley