The current loss of biodiversity has put 50,000 plant species at an elevated risk of extinction worldwide. Conserving at-risk species is often complicated by covariance or non-additivity among threats, which makes it difficult to determine optimal management strategies. We had a unique opportunity to demographically quantify covariance and non-additive effects of more threats on more rare plant species than ever before in a single analysis. We used 1,082 population monitoring reports from 186 populations across three US states of 27 rare, herbaceous plant species collected over 15 years by citizen scientists. We found a significant three-way interaction on annual growth rates such that rare plant population sizes were reduced by 46% during the time immediately post-disturbance when populations were also browsed by deer and had high level of woody species encroachment. This non-additive effect should be considered a major threat to the persistence of rare plant species. Our work highlights the need for comprehensive, multi-threat assessments to determine optimal conservation actions. Article impact statement: Multi-threat assessment reveals an interactive effect with a dangerously large negative impact on rare plant species' viability. This article is protected by copyright. All rights reserved.

中文翻译：

---

对稀有植物物种的威胁之间的非累加效应

目前生物多样性的丧失使全世界 50,000 种植物物种面临更高的灭绝风险。由于威胁之间的协方差或非可加性，保护濒危物种通常很复杂，这使得很难确定最佳管理策略。在一次分析中，我们有一个独特的机会在人口统计上量化协方差和更多威胁对稀有植物物种的非加性影响。我们使用了公民科学家在 15 年内收集的来自美国三个州 27 种稀有草本植物物种的 186 个种群的 1,082 份种群监测报告。我们发现年增长率存在显着的三向相互作用，因此在扰动后立即种群也被鹿捕食并且木本物种侵占程度高时，稀有植物种群大小减少了 46%。这种非累加效应应被视为对稀有植物物种持久性的主要威胁。我们的工作强调需要进行全面的、多威胁的评估，以确定最佳的保护行动。文章影响声明：多威胁评估揭示了一种交互影响，对稀有植物物种的生存能力具有危险的巨大负面影响。本文受版权保护。版权所有。我们的工作强调需要进行全面的、多威胁的评估，以确定最佳的保护行动。文章影响声明：多威胁评估揭示了一种交互影响，对稀有植物物种的生存能力具有危险的巨大负面影响。本文受版权保护。版权所有。我们的工作强调需要进行全面的、多威胁的评估，以确定最佳的保护行动。文章影响声明：多威胁评估揭示了一种交互影响，对稀有植物物种的生存能力具有危险的巨大负面影响。本文受版权保护。版权所有。