Human societies depend on an Earth System that operates within a constrained range of nutrient 68 availability, yet the recent trajectory of terrestrial nitrogen (N) availability is uncertain. 69 Examining patterns of foliar N concentrations ([N]) and isotope ratios (δ 15 N) from more than 42,000 samples acquired over years, here we show that foliar [N] declined by 8% and foliar δ 15 N declined by 0.8 -1.9 ‰. Examining patterns across different climate spaces, foliar δ 15 N declined across the entire range of MAT and MAP tested. These results suggest declines in N supply relative to plant demand at the global scale. In all, there are now multiple lines of evidence of declining N availability in many unfertilized terrestrial ecosystems, including declines in δ 15 N of tree rings and leaves from herbarium samples over the past 75-150 years. 76These patterns are consistent with the proposed consequences of elevated atmospheric CO 2 and longer growing seasons. These declines will limit future terrestrial C uptake and increase nutritional stress for herbivores. 235 much. Preventing these declines in N availability further emphasizes the need to reduce 236 anthropogenic CO 2 emissions.Data and code availability. The datasets generated during and/or analysed during the current study are available in the Dryad repository [link to be generated upon acceptance]. All code used for statistical analyses and figure generation are available on Dryad (XXX).

Extinction risk for 101 valid species and 18 unique genetic lineages of native freshwater fishes of South Africa was assessed in 2016 following the IUCN Red List criteria. An additional five species (three new species that were described and two species that were revalidated subsequent to the 2016 assessments) were assessed in the present study. A synthesis of the outcome of the assessments of the 106 valid species and 18 genetic lineages indicates that 45 (36%) of South Africa's freshwater fish taxa are threatened (7 Critically Endangered, 25 Endangered, 13 Vulnerable). Of the remaining taxa, 17 (14%) are listed as Near Threatened, 57 (46%) are Least Concern and five (4%) are Data Deficient. More than 60% of the endemic taxa are threatened. The Cape Fold Ecoregion has the highest proportion of threatened taxa (67%) due to the existence of a unique assemblage of narrow‐range endemic species. Galaxias and Pseudobarbus have the highest number of highly threatened taxa as most of the species and lineages in these genera are classified as either CR or EN. Major threats to the native freshwater fishes of the country are invasive fish species, deterioration of water quality, impoundments and excessive water abstraction, land use changes and modification of riverine habitats. Immediate conservation efforts should focus on securing remnant populations of highly threatened taxa and preventing deterioration in threat status, because recovery is rare. Accurate delimitation of species boundaries, mapping their distribution ranges, improved knowledge of pressures and long‐term monitoring of population trends need to be prioritised to generate credible data for the 2026 IUCN threat status assessments and designation of important fish areas as part of the National Freshwater Ecosystem Priority Areas (NFEPA) initiative.

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Freshwater systems and their associated biodiversity are among the most threatened ecosystems globally. The greatest threats to freshwater fishes are the introduction and spread of non-native species, pollution, habitat degradation and loss, and overexploitation. While many regions across the world contain extensive networks of protected areas, these are largely ineffective for protecting riverine systems and their biodiversity. This is because they were designed with the aim of prioritising conservation of terrestrial biodiversity, with limited or no consideration for aquatic systems. The Cape Fold Ecoregion, located within the Western and Eastern Cape Provinces of South Africa, is home to the highest percentage of threatened freshwater fishes in the country. The region has an extensive protected area network that protects a wide array of ecosystems, but limited information exists on the role of protected areas in conserving the endemic freshwater fish fauna of this region. This study evaluated the value of protected areas for protection of freshwater fishes in the Western Cape Province by setting species conservation targets and then intersecting species distribution data with protected area polygons. Conservation targets were set to protect the minimum viable population required for long-term persistence, with a minimum of 10 subpopulations as a target. This, along with other factors such as population viability and protected area effectiveness was used to determine whether a species was effectively protected by the current protected area network. Species were classified into one of four categories; (1) “well protected,” (2) “moderately protected,” (3) “poorly protected,” and (4) “not protected.” Our results indicate that the majority of native fishes are inadequately protected within the current protected area network in the province. This is mainly a result of the linear nature of riverine ecosystems that exposes them to impacts and threats that emanate from outside of the protected area. These limitations are not unique to the CFE, and our findings have broader implications as they highlight the need for integrating both the riverine and terrestrial ecosystems in the design, expansion and management of protected areas. This will enhance and maximise conservation and protection of riverine systems and their unique biodiversity.