Unifying spatial scaling laws of biodiversity and ecosystem stability.

While both species richness and ecosystem stability increase with area, how these scaling patterns are linked remains unclear. Our theoretical and empirical analyses of plant and fish communities show that the spatial scaling of ecosystem stability is determined primarily by the scaling of species asynchrony, which is in turn driven by the scaling of species richness. In wetter regions, plant species richness and ecosystem stability both exhibit faster accumulation with area, implying potentially greater declines in biodiversity and stability following habitat loss. The decline in ecosystem stability after habitat loss can be delayed, creating a stability debt mirroring the extinction debt of species. By unifying two foundational scaling laws in ecology, our work underscores that ongoing biodiversity loss may destabilize ecosystems across spatial scales. Editor's summary: The number of species in an ecosystem relates to several other key properties, including biomass and stability across time. Two studies in this issue combine theory with existing data on multiple taxonomic groups to understand these relationships. Pigot et al. show that biomass generally increases with species richness because large-bodied species tend to be rare. Liang et al. show that ecosystem stability increases with area because of its relationship with biodiversity. Larger areas tend to have more species and more asynchrony between species, leading to greater stability. Together, these studies provide further insight into how biodiversity affects other ecosystem properties. —Bianca Lopez INTRODUCTION: The positive relationship between biodiversity, measured as species richness, and the temporal stability of ecosystems is well-established in theory and empirical work at small spatial scales. However, whether and how these insights can be generalized to broader spatial scales—in which ecosystem management is typically applied—remains elusive. Both species richness and ecosystem stability increase with area, described by species−area relationships (SAR) and ecosystem stability−area relationships (EStAR), respectively. Integrating these spatial scaling patterns allows us to scale biodiversity–stability relationships from small to large areas and to predict how biodiversity and ecosystem stability respond to habitat loss and anthropogenic environmental changes. RATIONALE: To understand the link between SAR and EStAR—specifically their log-log slopes (SAR and EStAR)—we develop a new theoretical framework that partitions the spatial scaling of ecosystem stability into two components: the spatial scaling of average species stability and that of species asynchrony. Using this framework, we employ spatial ecological models to illustrate how ecosystem stability and its two components scale with area and respond to habitat loss, as well as how these scaling patterns are mediated by changes in species richness. We further investigate the scaling patterns of species richness and ecosystem stability using two extensive datasets: plant communities from the National Ecological Observatory Network (NEON) in the US and fish communities from the global dataset RivFishTIME. RESULTS: Theoretical models predict that as the sample area increases, both ecosystem stability and average species stability generally increase, whereas species asynchrony may either increase or decrease. Ecosystems with a steeper accumulation of species richness with area (higher SAR) demonstrate a faster increase in stability with area (higher EStAR). The positive correlation between SAR and EStAR emerges because higher species richness generates more asynchronous dynamics and thus stronger stabilizing effects at larger scales. Following habitat loss, species richness gradually declines over time, exhibiting an extinction debt. This extinction debt of species in turn leads to a delayed decrease in ecosystem stability, which we term stability debt. A larger debt in ecosystem stability occurs when there is a larger extinction debt. Empirical analyses reveal patterns consistent with theoretical predictions. For both plants and fishes, ecosystem stability and average species stability increase with area, whereas species asynchrony either increases or decreases with area across NEON sites and river basins. The scaling exponents of biodiversity and ecosystem stability (SAR and EStAR) are positively correlated, primarily due to greater species asynchrony as species richness increases with increasing scales. In plant communities, the scaling exponents of both biodiversity and ecosystem stability increase with precipitation, whereas those of fish communities are unaffected by climatic factors. CONCLUSION: By integrating two foundational scaling laws in ecology, SAR and EStAR, our study underscores the broad applicability of biodiversity–stability relationships across spatial scales. It predicts that ongoing biodiversity loss could lead to ecosystem destabilization at large scales. Habitat loss and landscape homogenization are also anticipated to destabilize ecosystems. The destabilization following habitat loss may unfold gradually over time, resulting in a stability debt analogous to the extinction debt of species. Understanding how anthropogenic activities influence the scaling properties of biodiversity and ecosystem stability is crucial for sustainable ecosystem management in the era of rapid environmental change. Analyses reveal unified spatial scaling patterns of biodiversity and ecosystem stability.: Ecosystem stability−area relationship (EStAR) can be partitioned into average species stability−area (SStAR) and species asynchrony−area (AsAR) relationships. Theoretically, species-area relationship (SAR) influences EStAR through SStAR and AsAR. Empirical data demonstrate positive correlations between SAR and EStAR, primarily driven by AsAR. Habitat loss may gradually reduce ecosystem stability over time, resulting in a stability debt. [ABSTRACT FROM AUTHOR]