On a stunning 15 km stretch of Portuguese coast two special cliff plants found nowhere else on earth are facing extinction. One threat is the spread of the ice plant, an invasive species that can have a devastating impact on the ecosystem. Another issue is that many park visitors are unaware that rare plants exist here and so may not take enough care to protect them. A further challenge to conservation is access. The endangered plants are perched on steep cliff faces making access to monitor them difficult.
To address these challenges we are organising invasive plant removal events. Helping hands are coming from local rock climbers and cavers, joining us as volunteers united by their passion to protect local biodiversity. These events are also a way of spreading awareness and engaging different groups in a dialogue about what can be done for these species. For the monitoring, we will be using a drone to detect the rare plants and to document changes in the vegetation as a result of our efforts to remove the invasive ice plant.
By protecting these precious plants we are helping reduce biodiversity loss and trying to treasure nature in all its glorious forms.
Invasive plant removal and community engagement
We are organizing events with local volunteers to help remove the invasive ice plant from the area where it is competing with the rare cliff plants. This is done by manually pulling the plants and removing them from the area. With these events we are aiming to:
- stop the invasion before it spreads further and control efforts become unfeasible;
- take direct action to restore diverse cliff plant communities (similar efforts have been successful elsewhere);
- spread awareness about these species to prevent any damage by park visitors;
- encourage dialogue between all the groups involved in protecting, studying and enjoying the area.
Monitoring with a drone and photogrammetry
We will be capturing drone images to survey inaccessible cliffs and ensure we have the evidence needed to guide our conservation actions. We expect the technology will have multiple uses:
- detecting the presence of rare plant species in hard to access locations;
- monitoring the distribution of the invasive ice plant and use this data to coordinate removal events;
- monitor the vegetation before and after ice plant removal to check if the vegetation is recovering as expected or if further intervention is needed.
Learn more about how and why we want to protect these plants
We've described the project itself above, but read on to see why this is so important.
Two plant species in risk of extinction
For some plants, the cliffs of Cabo Espichel are the ideal refuge from human disturbance and from other species that would outcompete them elsewhere. Two of these plant species have their entire global distribution restricted to this 15 km stretch of coastline and have been listed as endangered in the recently published Red List of Vascular Plants of continental Portugal.
Convolvulus fernandesii is a species of vine that grows on the cliff faces and at their base, sometimes climbing over other plants and shrubs. It puts out beautiful white flowers in the spring and in the summer its bright green leaves turn yellow. It is extremely rare with the latest estimate putting the total number of mature individuals at 500.
Euphorbia pedroi is a sub-succulent plant that is adapted to dry conditions which can attain up to 2m in height and more than 2m in width. Its leaves have a very distinct tone of green before they are shed every year during the heat of summer. Although it appears to be more numerous than C. fernandesii, there are only three known subpopulations in the area and it is unclear to what extent these are connected.
The extreme scarcity of each of these plants makes this a worthwhile mission to ensure their uniqueness remains instead of losing them forever.
Threats that are thought to be affecting both species include:
- increases in the frequency and intensity of droughts;
- trampling by unaware park visitors;
- the spread of the invasive ice plant (Carporboruts edulis).
Other rare plants
Other than the two narrow endemics, this part of the coast is very rich in plant diversity with about 1400 plant species recorded. Some of these are rare in Portugal and have been identified as a conservation priority by the Portuguese Botanical Society including:
- Scrophularia sublyrata
- Limonium echioides
- Withania frutescens
- Lavatera maritima
- Patellifolia patellaris
- Volutaria crupinoides
How did the invasive plant get here?
One serious threat for these rare species is the spread of ice plant (Carpobrous edulis) in the area. This is an invasive succulent plant that forms dense mats which change the soil composition and displace native species that have been evolving together for millennia. It can spread rapidly on dunes and coastal cliffs wiping out entire plant communities. As in other European countries, the species was introduced in Portugal during the 1900s because it was thought to help prevent coastal erosion. It is currently widespread along the Portuguese coast.
Why local rock climbers are joining us
Rock climbers are among the people that spend the most time exploring these cliffs and so are more likely to encounter these rare species. By spreading awareness among the climbing community we want to help reduce the chances that someone will damage these plants due to a lack of knowledge. What’s more, rock climbers are comfortable navigating these hard to access locations so they make ideal volunteers to help us plan and carry out interventions in the area. Having said this, everyone is welcome to join and we hope to get a wide range of people excited about plants and other cliff-dwelling biodiversity!
Using a drone for cliff plant monitoring
Current methods for monitoring these rare endemic species are very time consuming making it impractical to carry out population surveys with the accuracy and frequency needed to detect population trends and threats. Both species have a very narrow range but their habitat is very hard to access.
If no other monitoring approach is used, we would have to invest substantial time in continuously monitoring these populations. Accurate population size estimates would require very thorough sampling using abseiling and rock climbing techniques. Other than being logistically complex, this type of survey would be intrusive and could inadvertently disturb the cliff ecosystem.
To address this, we are using a drone to capture high resolution images which can later be processed to detect where the individuals of each species are present. After being validated and refined, we hope this approach will provide a reproducible and cost effective way to monitor the abundance and distribution of these rare species.
We also aim to use the drone and photogrammetry software to create orthophotomaps of the areas where C. edulis is to be removed. The resulting maps will help to plan the removal events but, more importantly, they provide a baseline scenario for monitoring the impact of this intervention on native vegetation. By creating the same maps every year, we hope to capture the process of recolonization by native vegetation. These surveys may demonstrate the success of the intervention or a failure of native plants to recolonize the area which would suggest that assisted revegetation may be appropriate. Finally, we expect the maps will prove useful as a way of identifying C. edulis resprouts that could be missed otherwise.
The partnerships making this project possible
We are getting all kinds of partners together for this project. The local rock climbing community and the cavers from NECA are contributing as volunteers with their local knowledge, sweat and hard work in our invasive plant removal events.
Pix4D, a drone mapping software company, will be helping us process the drone imagery for our monitoring objectives.
The Portuguese Botanical Society is contributing with their expertise and the local park authorities (ICNF) are helping ensure our efforts fit into the broader conservation strategy for this protected area.
Sources & further reading
- “Lista Vermelha da Flora Vascular de Portugal Continental” - Sociedade Portuguesa de Botânica, Associação Portuguesa de Ciência da Vegetação – PHYTOS e Instituto da Conservação da Natureza e das Florestas (coord.)
- “Monographs of invasive plants in Europe: Carpobrotus” - Botany Letters