One hundred years of climate change in Mexico

Introduction Climate change has been recognized as one of the major drivers of socio-environmental dis- ruption in recent years [1,2] due to its strong effect on demographic, geographic and ecosys- tem processes [1,3–6]. Climate change acts in synergy with other environmental disruptive factors, such as habitat loss, pollution, overexploitation, and invasive species [7,8]. Currently, climate change studies in biodiversity have strongly focused on future projections with less attention to current and recent historical climate change impacts that could provide valuable information to guide conservation efforts. The climate has been changing globally and non-uniformly since the mid-20th century. Pat- terns of climate change are dynamic and highly heterogeneous across the planet: global mean surface temperature has increased around 0.85˚C in the last 130 years, and since the 1970s, precipitation has generally increased in latitudes beyond 30˚ and decreased in the tropics [9,10,11]. One of the main inputs for regional or global climate change assessments are interpolated climate surfaces at a high spatial resolution of both present-day/historical climate and down- scaled surfaces of future climate projections [12]. High-resolution gridded climate surfaces (referred to as “climate surfaces” from here on) for global land areas have been useful for assessing how climate change affects biodiversity [13]. Although global databases, such as WorldClim and Climond, are freely available [12,14], these databases present some shortcom-

ings that impede evaluating the historical climate change and their impacts on biodiversity; for example, they span only a single period of time in the late 20th century. Furthermore, the qual- ity and reliability of global databases are compromised in many regions because the data from weather stations used for producing global interpolations generally come from open, public databases, whereas in some places–such as Mexico–there is more information available, but needs to be requested. Also, there is more time and effort devoted to detecting and correcting errors in databases if people are focused on a particular region than worldwide; for example, reconciling location (coordinates) with elevation of stations has been more thoroughly done at regional levels [14,15]. Until now, gridded climate surfaces for Mexico are only readily avail- able for single time slices [15–17], so they are not suitable for evaluating temporal climatic changes. Regardless, time series information at the level of climate stations is available for cli- mate change analysis [18,19], although some regions across the country lack adequate spatial coverage. One option to overcome this limitation is to analyze data from climatic surfaces at different periods from the recent past and the present in an attempt to understand where, when and to what degree the climate has been changing, in an effort to evaluate its environmental and social implications [2,20–28]. For instance, combining data of climate surfaces with species

inventories can be useful for detecting drivers of change in biological communities [28,29] and responses of biodiversity to climate change [30]. Historic climate surfaces can be used to iden- tify areas that have been under the effect of climate change for some time to analyze the response and resilience of natural and social subsystems [31]. Furthermore, coupling this information with future projections can help to inform decision-makers [32–34]. This approach has been successful in Australia, where historical climate data facilitated conserva- tionists to detect recent range shifts in bird communities that may be informative for future biotic responses [35]. To date, most studies evaluating the impacts of climate change on biodiversity have focused, first, on future projections rather than under a retrospective approach, and second, on individ- ual species and ecosystems [1], and not at other organizational levels [36]. A more inclusive approach would be to assess climate change impacts in biogeographic units, which represent PLOS ONE Historical climate change in Mexico PLOS ONE | https://doi.org/10.1371/journal.pone.0209808 July 16, 2020 2 / 19 Competing interests: No authors have competing interests.