The speed of change in climate and land cover is associated with the speed of biodiversity changes in avian assemblages of the United States

PLOS One | https://doi.org/10.1371/journal.pone.0330153 August 29, 2025 2 / 20 Nevertheless, climate change is not new, and studies in fossil avifauna and pollen records show how species assemblages of birds and plants changed around 12,000 years ago, in response to these changes in climate [6,7]. What is alarming, however, is the rapid rates at which climate changes are occurring and their predicted accel- eration in the future [8–10]. For example, in the last 200 years, abrupt vegetation changes were significantly higher than at any time in the previous 7,000 years [11]. Moreover, under current best estimates of future climate change, one in six species will face extinction by the end of this century [12]. Land use and land cover (LULC) change is another driver of biotic homogeni- zation linked to population declines and species loss [13,14], which poses threats 3–10 times higher in magnitude than those due to climate change [15]. However, the relative importance of these two environmental factors as drivers of biodiversity loss in terrestrial ecosystems appears to be scale-dependent; changes in LULC have a greater impact on population trends while changes in climate affect species assem- blage composition [16]. Nevertheless, the relative importance of these factors may switch over time: meaning that the projected impacts of climate change on vertebrate biodiversity could match or exceed the effect of historical LULC change by the year 2070 [17]. Further, other authors have found that the relative importance of climate

change versus LULC change as drivers of change in biodiversity varies across biodiversity dimensions and habitat or ecoregion types [18,19]. This underscores the importance of considering multiple environmental factors in community ecology since threats to species are not discrete, and the majority of assemblages experience a combination of changes in climate and LULC [15]. Changes in climate and LULC are interrelated [20,21] and can interact [22,23]. Their simultaneous effect has been investigated across multiple taxa and biomes [24–32]. Changes in these two drivers could result in no change of the species assemblages, but could conversely lead to either biotic homogenization or heter- ogenization (for example, [25,31]), potentially impacting the stability and resilience of the ecosystem, as well as its functions and the services it provides [23,33–36]. It is important, however, to also understand how rapidly natural assemblages are responding to different rates of changes in environmental conditions. Studies comparing climate velocity with species responses have found that whether species’ paces match – or lag behind – climate change is species-specific [37–39]. Just a few studies have considered the combined velocities of climate and LULC change [40,41]. We have previously found that within-ecoregion changes in avian richness and assemblage dissimilarity have occurred rapidly in the last 30 years in the United States [42]. However, the effect of different rates of changes in cli- mate and LULC on the rate of change of biodiversity of current species assemblages,

where species may or may not have tracked those changes, has yet to be assessed. Further, the rates of change in climate and LULC may be quite different across ecore- gions or biomes [8,41]. For example, in the United States, for year 2050, relatively rapid changes in both climate and LULC are predicted for the Midwest region, while relatively rapid changes in climate but not in LULC are predicted for the Southwest region [41]. Thus, the mechanisms through which avian communities respond to Group. Parameter-elevation Regressions on Independent Slopes Model (PRISM) Gridded Climate Data. Recent years (1981 -2020). [https://prism.oregonstate.edu/recent/] - U.S. Geological Survey: Modeled Historical Land Use and Land Cover for the Conterminous United States: 1938-1992 [https://doi. org/10.5066/F7KK99RR] - U.S. Geological Survey: Conterminous United States Land Cover Projections - 1992 to 2100. [doi: 10.5066/P95AK9HP] -U.S. Geological Survey: North America Elevation. [http://www.cec.org/ north-american-environmental-atlas/eleva- tion-2007/] - Author-generated code scripts for the statistical analysis in the manuscript are available in https://github.com/Marlen86/ biodiv_rate_change.git Funding: RFCUNY Interdisciplinary Climate Crisis. Grant Number: 80210-10 25 (L.L.M. is one of the Principal Investigators). URL: https://www.cuny.edu/research/research-de- velopment-programs/faculty-programs/ internal-funding/interdisciplinary-re- search-grant-program/ NSF Office of polar programs (OPP) Grant number: 2011454. (L.L.M. is one of the Principal Investigators).

URL: https://www.nsf.gov/geo/opp The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist.