Global decline in nitrogen availability has consequences for many natural ecosystems

Declining nitrogen availability in many terrestrial ecosystems has widespread consequences for biodiversity and ecosystem functioning worldwide. In a Review, Rachel Mason and colleagues discuss the extent and consequences of nitrogen (N) decline, the human factors potentially driving it, and what might be done to help mitigate its damaging effects. “Akin to trends in atmospheric [carbon dioxide] and global temperatures, large-scale declines in N availability are likely to present long-term challenges that will require informed management and policy actions in the coming decade,” write Mason et al. Nitrogen is essential to life on Earth – it’s a key component of the plant proteins required to support the growth of plants and the animals that feed on them. Therefore, N availability in the environment has a strong influence on the structure and function of many ecosystems. While humans have more than doubled the global supply of reactive N through industrial and agricultural activities over the last century, much of this input has occurred in urban and agrarian areas. For areas not subject to anthropogenic N enrichment, however, a growing body of research suggests that N availability is declining in many terrestrial ecosystems worldwide. According to the authors, multiple environmental changes may be driving these declines, including elevated atmospheric carbon dioxide, rising global temperatures, and altered precipitation and ecosystem disturbance regimes. Reduced N availability can lead to changes in primary productivity in these ecosystems, impacting the diets of herbivores like insects, whose survival can have farther reaching impacts at higher trophic levels. Mason et al. highlight several ways that N decline can be monitored and mitigated but note that continued research is needed to inform management actions. “Given the potential implications of declining N availability for food webs, carbon sequestration, and other ecosystem functions and services, it is important that research, management, and policy actions be taken before the consequences of declining N availability become more severe,” write Mason et al.