دانلود رایگان مقاله یک ارزیابی منظم از تهدیدهای موثر بر گیاهان نادر ایالات متحده

ABSTRACT

Characterizing the distribution of threats facing species is a crucial, first step toward designing effective conservation strategy. The last comprehensive analysis of threats facing rare plants in the United States was conducted nearly 20 years ago. Here we systematically analyze the threats facing 2733 rare and vulnerable plants in the US using textual analysis of the most comprehensive database available. In the continental US plants are most commonly threatened by outdoor recreation (affecting 35% of species), especially from off-road vehicles (19%) and hiking and related activities (13%). The next-most common threats are from livestock (33%), residential development (28%), non-native invasives (27%), and roads (21%). In Hawaii invasives threaten 95% of species followed by increases in fire intensity/frequency (26%) then livestock (19%). Multivariate analyses indicate threats do not form distinct “syndromes” (clusters of threats) but rather a single “mega-syndrome” with high degrees of overlap between most threats. We also compared the prevalence of threats to the distribution of research effort. Nearly 75% of threats are understudied relative to their prevalence, including five of the six most common threats while a few rare threats (missing species like pollinators; pathogens; logging; climate-induced ecosystem movement; and crop-based agriculture) receive most of the attention. In comparison to a benchmark assessment from 1998 (Wilcove et al. BioScience 48:607-615) we find little difference in threat prevalence, though temporal trends suggest increasing frequency of nearly all threats. Overall rare plants in the US are affected by a dense network of threats across which research attention is disproportionately directed.

5. Conclusions

In descending order, the most common threats to plants in the continental US include outdoor recreation (especially from ORVs and hiking and related activities), livestock, invasives, then construction and maintenance of roads and railroads plus their berms. Alarmingly, there is some evidence that these threats are either understated or increasing in prevalence. None of these threats receive attention in the peerreviewed scientific literature that is proportionate to their actual prevalence in the United States. Our results paint a formidable conceptual and strategic challenge for conservation. Rare plants in the US face a complex “mega-syndrome” in which threats act coincidentally to affect non-exclusive groups of species. Thus there seems to be no simple, highly-effective strategy that can alleviate threats to the majority of species at once. Rather, integrated coarse-scale strategies like setting aside land for preservation combined with fine-scale strategies like spot control of invasives or educating and diverting recreationists within established parks will be necessary to address the diversity of threats facing plants in the United States. We do note that inspiring work is developing methods for addressing multiple threats at regional scales (e.g., Conlisk et al., 2013; Auerbach et al., 2015; Tulloch et al., 2016), but more work needs to be done to extend these techniques across scales. We hypothesize that mega-syndromes arise as a product of diverse patterns of land use and exploitation associated with complex economies. If this is indeed the case, then novel conceptual tools and plans of action are required to address the mega-syndrome of threats facing rare plants.