Drivers of urban biodiversity in Mexico and joint risks from future urban expansion, climate change, and urban heat island effect

Table 1. Ecological and socioeconomic processes approximated by a series of variables that are linked with urban species richness in Mexican cities. Hypothesis Variable Prediction Explanation City size Urban area (log10Area) Larger cities are expected to maintain more species than smaller cities Species-area relationships (SAR) can be interpreted under MacArthur & Wilson’s [36] equilibrium theory of island biogeography theory. Larger cities are expected to exhibit more species, but some thresholds can emerge in SARs [35]. These thresholds are likely related to a minimum city size requirement to maintain multiple species. Gross domestic product (GDP) Cities with higher GDP are expected to maintain more species than cities with lower GDP. A proxy of economic development that might be related to government and private investment in more green spaces and economic resource allocation to implementation of specific urban conservation strategies. Human total density (Dens_total) / Human rural density (Dens_urban) We expect municipalities with high human total and rural density to contain a smaller number of species. Species richness and human density are positively correlated at coarse-grain spatial scales but negatively at fine-grain scales [87, 88]. The positive relationship at larger scales is mediated by energy availability because human settlements are in high- energy regions where resource availability is larger [89]. Habitat Intactness Urban tree height (TreeHeight) Cities with higher tree heights are expected to maintain more species than cities with

lower tree heights. Tree height is a proxy of available green space, either as urban protected areas or urban parks in each city. Natural protected areas (area) (log10_ANPs_areas) Cities with higher protected areas are expected to maintain more species than cities with smaller protected areas. The cumulative area for the Protected Area Network system in each city is a proxy of high species richness and better levels of conservation management. Remnant vegetation (VegtRem) Municipalities with higher remnant vegetation are expected to have adjacent urban areas with more species. Remnant vegetation is a strong driver of species richness [90]. Human impact Marginalization Municipalities with higher marginalization are expected to exhibit fewer species richness. The marginalization index integrates different elements of poverty, education, housing, population distribution, and incomes in rural areas [55]. Higher marginalization means more social vulnerability in rural areas, and it is expected that more marginalized municipalities overlap with more biodiversity Mexican hotspots [91–93] Percentage of the population working in the primary sector (porPob) Municipalities with more people in the sector are expected to have urban areas with higher species richness. This metric refers to the percentage of people relying on agricultural production for self- consumption and income. This is a proxy of more rural areas in each municipality and can be linked with high species richness in urban areas by mass effects [94], rescue effects [95], or source-sink

metacommunity dynamics [96, 97] Demographic pressure index (IPD) We expect that municipalities with higher demographic pressure are expected to contain fewer species. More people in rural-urban areas are exerting more pressures on natural resources and modifying land use, which promotes a less accumulation of species in rural-urban areas. Habitat diversity Topographic complexity (TPI) Urban cities located in more topographic complexity regions are expected to exhibit higher species richness. Mountain systems with higher topographic complexity tend to exhibit many species [98, 99]. Habitat uniformity (Evenness) Cities with greater habitat heterogeneity are expected to have more species. Habitat heterogeneity is recognized as a direct driver of species richness across space and time. Habitat variation facilitates more niche space and, therefore, increases the number of co-occurring species in a site [100–102]. (Continued) PLOS ONE Urban biodiversity and anthropogenic pressures PLOS ONE | https://doi.org/10.1371/journal.pone.0308522 October 4, 2024 4 / 19