Human Impacts, Plant Invasion, and Imperiled Plant Species in California

Seabloom, Eric W.; Williams, John W.; Slayback, D. A.; Stoms, David M.; Viers, Joshua H.; Dobson, Andy

doi:10.1890/1051-0761(2006)016[1338:hipiai]2.0.co;2

Cited by 152 publications

(149 citation statements)

References 61 publications

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“…the increasing wildland-urban interface in California, where houses intermingle with undeveloped vegetation (Radeloff et al, 2005). This interface represents not only habitat fragmentation but associated human habitation promotes the introduction of invasive alien species (Seabloom et al, 2006) and intensifies the severity of wildfire (Spyratos et al, 2007). Similarly, modifications of natural fire regimes is promoting the invasion of alien plant species (Keeley et al, 2005;Vogiatzakis et al, 2005) and altering successional trajectories of recovering plant communities (Franklin et al, 2005) in some mediterranean regions, while in the Chilean matorral, which is poorly adapted to fire, increasing numbers of anthropogenic fires are causing disruption to native plant species and communities (Montenegro et al, 2004).…”

Section: Conserving Biodiversity In the Mediterranean Biome In The Fumentioning

confidence: 99%

Threats and biodiversity in the mediterranean biome

Underwood

Viers

Klausmeyer

et al. 2009

Diversity and Distributions

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319

212

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Aim Global conservation assessments recognize the mediterranean biome as a priority for the conservation of the world's biodiversity. To better direct future conservation efforts in the biome, an improved understanding of the location, magnitude and trend of key threats and their relationship with species of conservation importance is needed.Location Mediterranean‐climate regions in California‐Baja California, Chile, South Africa, Australia and the Mediterranean Basin.Methods We undertook a systematic, pan‐regional assessment of threats in the mediterranean biome including human population density, urban area and agriculture. To realize the full implications of these threats on mediterranean biodiversity, we examined their relationship with species of conservation concern: threatened mammals at the global scale and threatened plants at the subecoregional scale in California, USA.Results Across the biome, population density and urban area increased by 13% and agriculture by 1% between 1990 and 2000. Both population density and urban area were greatest in California‐Baja California and least in Australia while, in contrast, agriculture was greatest in Australia and least in California‐Baja California. In all regions lowlands were most affected by the threats analysed, with the exception of population density in the Chilean matorral. Threatened species richness had a significant positive correlation with population density at global and subecoregional scales, while threatened species were found to increase with the amount of urban area and decrease as the amount of natural area and unfragmented core area increased.Main conclusions Threats to mediterranean biodiversity have increased from 1990 to 2000, although patterns vary both across and within the five regions. The need for future conservation efforts is further underlined by the positive correlation between species of conservation concern and the increase in population density over the last decade. Challenges to reducing threats extend beyond those analysed to include human–environmental interactions and their synergistic effects, such as urbanization and invasive species and wildfires.

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Section: Conserving Biodiversity In the Mediterranean Biome In The Fumentioning

confidence: 99%

Threats and biodiversity in the mediterranean biome

Underwood

Viers

Klausmeyer

et al. 2009

Diversity and Distributions

Self Cite

319

212

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“…The potential for increased invasion due to these time lags has been termed invasion debt (Bennett et al, 2013;Essl et al, 2011;Gilbert & Levine, 2013;Rouget et al, 2016;Seabloom et al, 2006), which consists of four phases: introduction, establishment, spread, and impact (Rouget et al, 2016). Invasion debt in this analysis focuses on potential establishment within the continental U.S. based on the current invasive species pool, and can be generated by species that have not yet spread to the full extent of their potential range or low infilling of the potential range.…”

Section: Introductionmentioning

confidence: 99%

Out of the weeds? Reduced plant invasion risk with climate change in the continental United States

Allen

Bradley²

2016

Biological Conservation

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Identifying invasion risk is critical for regional prioritization of management and monitoring, however, we currently lack a comprehensive assessment of the invasion risk posed by plants for the United States. We aim to quantify geographic invasion risk for currently established terrestrial invasive plants in the continental U.S. under current and future climate. We assembled a comprehensive occurrence database for 896 terrestrial invasive plant species from 33 regional collections of field and museum data and projected species ranges using MaxEnt species distribution models based on current (1950-2000 average) and future (2040-2060 average) climate. We quantified geographic invasion risk as differences in species richness, invasion debt, range infilling, and identification of hotspots. Potential invasive plant richness was higher than observed richness, particularly in eastern temperate forests, where as many as 83% of species with suitable climate have not yet established. A small percentage (median = 0.22%) of species' potential ranges are currently occupied by them. With climate change, potential invasive plant richness declined by a median of 7.3% by 2050. About 80% of invasive plant hotspots were geographically stable with climate change, with the remaining 20% shifting northward. Invasion hotspots and current invasion debt reveal extensive, ongoing risk from existing invasive plants across the U.S., particularly in the Southeast. Climate change alters the spatial distributions of focal species for monitoring and is likely to reduce overall invasion risk in many areas. Early detection and rapid response programs could be most effective in stemming the spread of invasive plant species in areas with increased risk under climate change, while areas with persistent high risk are candidates for containment and control. The areas with reduced risk are prime locations for invasion of new imports from tropical and subtropical climates, highlighting the simultaneous need for prevention strategies.

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“…For example, many oceanic island systems, including large archipelagos such as New Zealand and Hawaii, are now estimated to contain 100% more plant species than they did prior to human colonization (Sax and Gaines 2008). Continental regions such as California and South Africa have also experienced large increases in regional plant species richness (Macdonald and Richadson 1986, Sax 2002, Seabloom et al 2006. Such increases are not necessarily expressed at the local scale, however.…”

Section: Introductionmentioning

confidence: 99%

Novel forests maintain ecosystem processes after the decline of native tree species

Mascaro

Hughes

Schnitzer

2012

Ecological Monographs

103

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Abstract. The positive relationship between species diversity (richness and evenness) and critical ecosystem functions, such as productivity, carbon storage, and nutrient cycling, is often used to predict the consequences of extinction. At regional scales, however, plant species richness is mostly increasing rather than decreasing because successful plant species introductions far outnumber extinctions. If these regional increases in richness lead to local increases in diversity, a reasonable prediction is that productivity, carbon storage, and nutrient cycling will increase following invasion, yet this prediction has rarely been tested empirically. We tested this prediction in novel forest communities dominated by introduced species (;90% basal area) in lowland Hawaiian rain forests by comparing their functionality to that of native forests. We conducted our comparison along a natural gradient of increasing nitrogen availability, allowing for a more detailed examination of the role of plant functional trait differences (specifically, N 2 fixation) in driving possible changes to ecosystem function. Hawaii is emblematic of regional patterns of species change; it has much higher regional plant richness than it did historically, due to .1000 plant species introductions and only ;71 known plant extinctions, resulting in an ;100% increase in richness. At local scales, we found that novel forests had significantly higher tree species richness and higher diversity of dominant tree species. We further found that aboveground biomass, productivity, nutrient turnover (as measured by soil-available and litter-cycled nitrogen and phosphorus), and belowground carbon storage either did not differ significantly or were significantly greater in novel relative to native forests. We found that the addition of introduced N 2 -fixing tree species on N-limited substrates had the strongest effect on ecosystem function, a pattern found by previous empirical tests. Our results support empirical predictions of the functional effects of diversity, but they also suggest basic ecosystem processes will continue even after dramatic losses of native species diversity if simple functional roles are provided by introduced species. Because large portions of the Earth's surface are undergoing similar transitions from native to novel ecosystems, our results are likely to be broadly applicable.

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Human Impacts, Plant Invasion, and Imperiled Plant Species in California

Cited by 152 publications

References 61 publications

Threats and biodiversity in the mediterranean biome

Threats and biodiversity in the mediterranean biome

Out of the weeds? Reduced plant invasion risk with climate change in the continental United States

Novel forests maintain ecosystem processes after the decline of native tree species

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