How to protect plant species of conservation interest in urban landscapes?

Green spaces in cities form a new type of nature, created from ‘scratch’ or resulting from an irreversible change to natural habitats. Nature in the city is novel because all of its components are ‘artificially’ co-occurring; the soil, the water, the nutrients, and plant species which never existed together in natural habitats grow side by side in the city. Yet, this urban nature may serve as a valuable habitat for rare or endangered plant species, if one can design urban green spaces that are suitable for their growth and reproduction.

This specific question was addressed by Moustapha Itani, an MSc. student enrolled in the ecosystem management program in the department of landscape design and ecosystem management at the American University of Beirut. The plant species targeted by the study is the rare Lebanese endemic Stock (Mantour – Arabic, Matthiola crassifolia), which has persisted in Beirut city despite the rapid urban expansion. Considering that there are no vegetation description methods adapted to cities, especially when most cities, including Beirut, lack standard habitat classification systems, a combination of two methods normally used when studying natural areas was adopted; floristics (taxonomic identification and species abundance) and physiognomy (plant form, life form, layers, and sizes). The study area was a 6 km long and 2 km wide cape in the city of Beirut. Field explorations of green spaces in that area showed the Mantour growing along the shore in remnant spiny Mediterranean heaths, screes, sea cliffs, and rocky offshore islands, sandstone formation, limestone formations, and on (stabilized) coastal sand dunes. Inside the city, the plant grew near open sewers, in abandoned dump sites, through cracks in concrete walls and asphalt, on heaps of gravel, in street medians, and even out of the trunks of date and fan palms. The presence of the Mantour in all these different habitats reflected the species’ ability to grow in disturbed areas. This

By: S.N.Talhouk

finding complicated the interpretation of the floristic data because it did not clarify which species assemblages offer suitable habitats for the Mantour. In contrast, physiognomic data on life forms and abundance showed a pattern of relations with the target species. However, the physiognomy data did not reveal the identity of the favorable species. The findings became more informative when data from both methods were used in a stepwise approach, first mathematically classifying plants according to form, then sorting according to taxonomic identity. This exercise produced detailed information that pinpointed to urban habitats favorable to the target species. For example, the plant grew well in green spaces dominated by palms, low-lying succulents, or shrubs with scale-like leaves but it did not persist in green spaces dominated by turf grass, canopy trees, or vegetation that produces a significant litter. In addition to pointing to specific favorable plant associations, the study showed that an exotic and potentially invasive plant species (Carpobrotus edulis) was favorable to the growth of the Mantour. The outcome of the study was a plant selection palette that is not restrictive and does not enforce a native only policy for creating habitats favorable to the rare Lebanese Stock, Mantour. More importantly, we showed how the stepwise method developed in the study can serve as a tool to promote collaboration between plant ecologists, landscape architects, and landscape managers interested in reconciling conservation, socio-behavioral and aesthetic objectives.

Written by S.N. Talhouk. For more information please check: Itani M, Al Zein M, Nasralla N, Talhouk SN (2020) Biodiversity conservation in cities: Defining habitat analogues for plant species of conservation interest. PLoS ONE 15(6): e0220355. https://doi.org/10.1371/journal. pone.0220355