With more than 137,000 observations of fauna and flora, more than 4,300 species and 4,305 participants, the metropolitan region of La Paz topped the charts in the three categories of the City Nature Challenge 2022, in which more than 400 cities from 44 countries competed, and broke records for this international competition. Since the first edition of the City Nature Challenge in 2016, organized by the Los Angeles Natural History Museum and the San Francisco based California Academy of Sciences, no city ever passed 71,150 observations, nor 2,500 participants.

These impressive numbers are thanks to the momentum of a real citizens' movement that grew up around this competition. La Paz had previously participated in 2019, finishing second, third and eighth in the observations, participants and species categories, respectively. The COVID-19 pandemic frustrated efforts in 2020 and 2021. But this year, from April 29th to May 2nd 2022, hundreds of students from 68 schools that had been previously trained by the Wildlife Conservation Society (WCS) in coordination with the Vice-Ministry of Regular Education, the Biology Department and the Institute of Ecology of the Universidad Mayor de San Andrés, the National Museum of Natural History and the Municipality of La Paz, as well as university students, families, municipal officials and members of environmental groups joined this crusade to record images and videos of the fauna and flora of the metropolitan region of La Paz. The vast majority of the biodiversity records were made using mobile phones and the iNaturalist application, one of the world’s largest citizen science initiatives.

The metropolitan area of La Paz is made up of eight municipalities (La Paz, El Alto, Palca, Mecapaca, Achocalla, Viacha, Laja and Pucarani) and covers a marked altitudinal gradient, ranging from the 400 meters above sea level. in the Yungas and Amazonian foothill forests, through the inter-Andean valleys and puna, to the high Andes mountains, where the Illimani Andean peak and symbol of La Paz rises to 6,450 meters above sea level.  This gradient features a wide diversity of habitats, microclimates and species of flora and fauna; which largely explains the wide variety of species recorded during this year's challenge.

Outstanding records this year included the Phylodryas boliviana snake, endemic to Bolivia, that is little known and studied. This observation constitutes the fourth for this species in more than 20 years of research (Aparicio et al. 2015; Martínez 2017), and is the first-ever on iNaturalist. Over the history of the City Nature Challenge in La Paz (2019-2022) participants have generated over 150 records for two species of threatened and endemic smooth-throated lizards (Liolaemus aparicioi and L. forsteri), significantly increasing our understanding of their distribution in the La Paz valley.

The observation of an Orestias agassizii fish in a very well-preserved lagoon at 4,250 meters above sea level in the community of Pesqollo, 30 minutes from the government headquarters, is also an important record, as this is a species threatened by pollution and the introduction of invasive species such as trout and silversides. Equally impressive was the collection and sighting by the Bolivian National Herbarium in Sillutinkara (La Paz) of a small wild blackberry, Rubus conchyliatus, first recorded in Unduavi in 1913 but not seen since then in that sector. These examples show that participation in this type of contest, in addition to promoting public interest in nature, can also make a significant contribution to science.

Said WCS Senior Conservation Scientist, Rob Wallace: “All these achievements would not have been possible without the thousands of people who, cell phones and cameras in hand, left their homes to explore green spaces and reconnect with nature. An experience all the more important because it helps citizens in general, and children and young people in particular, to learn to look at plants and animals with curiosity and attention, while appreciating their importance for a healthy life. In a world that is ever more urban, initiatives that promote reconnections with Nature, including citizen science, will become more and more important. The City Nature Challenge is a wonderful example, and La Paz is leading the world on how to promote this activity.”