Controlling invasive alien shrub species, enhancing biodiversity and mitigating flood risk: A win-win-win situation in grazed floodplain plantations.

The high nature conservation value of floodplain ecosystems is severely threatened by invasive alien species. Besides adversely affecting native biodiversity, these species also pose a major threat from a wider socio-ecological perspective (e.g. 'roughness' increases flood risk). Finding options to control dense shrub layers consisting of invasive alien species is therefore of high priority for multipurpose management. We studied cattle grazing impacts on the cover, composition and diversity of the herb and shrub layers in floodplain poplar plantations along the Tamis river, Serbia. Non-grazed, moderately grazed, intensively grazed and resting place stands were sampled in five locations in three sampling points. Non-grazed stands had substantially higher cover of invasive alien shrub species (on average 65%) than moderately and intensively grazed stands, and resting places (5.17, 0.02 and 0.00%, respectively), but without considerable differences between the grazing intensity categories. The number of invasive alien species in the shrub layer decreased considerably from non-grazed to intensively grazed stands. Species composition in the herb layer changed from non-grazed to intensively grazed stands, while resting places differed substantially from the other categories. Total species richness, richness of native generalist herbaceous grassland species, and the cover of palatable grasses were the highest in moderately and intensively grazed stands. Our results suggest that cattle grazing in floodplains is effective at controlling invasive alien shrub species. Furthermore, continuous moderate or intensive grazing would contribute to multifunctional management of invaded floodplains by enhancing local biodiversity, reducing flood risk, and providing additional grazing areas for the local community.

Responses of New Zealand forest birds to management of introduced mammals.

Over the past 1000 years New Zealand has lost 40-50% of its bird species, and over half of these extinctions are attributable to predation by introduced mammals. Populations of many extant forest bird species continue to be depredated by mammals, especially rats, possums, and mustelids. The management history of New Zealand's forests over the past 50 years presents a unique opportunity because a varied program of mammalian predator control has created a replicated management experiment. We conducted a meta-analysis of population-level responses of forest birds to different levels of mammal control recorded across New Zealand. We collected data from 32 uniquely treated sites and 20 extant bird species representing a total of 247 population responses to 3 intensities of invasive mammal control (zero, low, and high). The treatments varied from eradication of invasive mammals via ground-based techniques to periodic suppression of mammals via aerially sown toxin. We modeled population-level responses of birds according to key life history attributes to determine the biological processes that influence species' responses to management. Large endemic species, such as the Kaka (Nestor meridionalis) and New Zealand Pigeon (Hemiphaga novaeseelandiae), responded positively at the population level to mammal control in 61 of 77 cases for species ≥20 g compared with 31 positive responses from 78 cases for species <20 g. The Fantail (Rhipidura fuliginosa) and Grey Warbler (Gerygone igata), both shallow endemic species, and 4 nonendemic species (Blackbird [Turdus merula], Chaffinch [Fringilla coelebs], Dunnock [Prunella modularis], and Silvereye [Zosterops lateralis]) that arrived in New Zealand in the last 200 years tended to have slight negative or neutral responses to mammal control (59 of 77 cases). Our results suggest that large, deeply endemic forest birds, especially cavity nesters, are most at risk of further decline in the absence of mammal control and, conversely suggest that 6 species apparently tolerate the presence of invasive mammals and may be sensitive to competition from larger endemic birds.

Respuestas de Aves Habitantes de Bosques Neozelandeses al Manejo de Mamíferos Introducidos Resumen En los últimos 1000 años, Nueva Zelanda ha perdido entre el 40% y 50% de las especies de aves. De estas extinciones, más de la mitad se puede atribuir a la depredación por mamíferos introducidos. Las poblaciones existentes de aves de bosque todavía están siendo depredadas por mamíferos, principalmente ratas, zarigüeyas y mustélidos. La historia de manejo de los bosques en Nueva Zelanda durante los recientes 50 años representa una oportunidad única porque un programa variado de control de mamíferos depredadores ha creado un experimento de manejo replicado. Realizamos un metaanálisis de las respuestas a nivel poblacional de las aves de bosque ante diferentes niveles de control de mamíferos registrados en toda Nueva Zelanda. Recolectamos datos de 32 sitios tratados de manera única y de 20 especies existentes de aves que representan un total de 247 respuestas poblacionales a tres intensidades de control de mamíferos invasores (cero, bajo y alto). Los tratamientos variaron desde la erradicación de los mamíferos invasores por vía de técnicas terrestres hasta la eliminación periódica de los mamíferos por medio de toxinas dispersadas por vía aérea. Modelamos las respuestas a nivel poblacional de las aves de acuerdo con los atributos de historia de vida importantes para determinar los procesos biológicos que influyen sobre las respuestas de las especies al manejo. Las especies endémicas grandes, como la kaka (Nestor meridionalis) y la paloma de Nueva Zelanda (Hemiphaga novaeseelandiae), respondieron positivamente a nivel poblacional al control de mamíferos en 61 de los 77 casos para especies con un peso ≥20 g comparado con 31 respuestas positivas de 78 casos para especies con un peso <20 g. El ave cola de abanico (Rhipidura fuliginosa) y la curruca gris (Gerygone igata), ambas especies endémicas someras, junto con cuatro especies no endémicas (el mirlo [Turdus merula], el pinzón [Fringilla coelebs], el acentor [Prunella modularis] y el pájaro de anteojos [Zosterops lateralis]) que arribaron a Nueva Zelanda en los últimos 200 años presentaron una tendencia hacia las respuestas negativas o neutrales al control de mamíferos (59 de 77 casos). Nuestros resultados sugieren que las aves endémicas grandes y que habitan en las profundidades del bosque, especialmente aquellas que anidan en cavidades, tienen el mayor riesgo de vivir una declinación en el futuro si el control de mamíferos se ausenta. A la inversa, nuestros resultados también sugieren que seis especies aparentemente toleran la presencia de mamíferos invasores y podrían ser vulnerables a la competencia generada por aves endémicas de mayor tamaño.

Managing River Fish Biodiversity Generates Substantial Economic Benefits in Four European Countries.

Ecosystems and biodiversity produce benefits to society, but many of them are hard to quantify. For example, it is unclear whether European societies gain benefits from experiencing rivers that host high native biodiversity. Without such knowledge, monetary investments into ecologically oriented river management plans are difficult to justify. The objective of this study was to reveal how the public in four European countries values ecological characteristics of domestic rivers and the outcomes of hypothetical river basin management plans designed to improve river ecosystems, particularly fish biodiversity. We conducted a choice experiment among the populations in Norway, Sweden, Germany, and France. We found similar preference structures in all countries with high marginal willingness-to-pay for improvements of abiotic river attributes (increased accessiblity of the river banks, improved bathing water quality, decreased river fragmentation). Citizens also benefited from certain fish species occurring in a river with native salmonid species being more valued than nonnatives, particularly in Norway, and from the degree of a river's native biodiversity. Welfare measures calculated for selected river basin management plans (policy scenarios) revealed societal benefits that were primarily derived from ecological river management whereas a scenario focusing on hydroelectricity production generated the lowest utility. We conclude that ecological river management may produce high nonmarket economic benefits in all study countries, particularly through the management of abiotic river attributes and the restoration of declining or extinct fish species. Our results help to inform decisions on restoration efforts by showcasing the benefits that these measures have for the public.

A city-scale assessment reveals that native forest types and overstory species dominate New York City forests.

Cities are increasingly focused on expanding tree canopy cover as a means to improve the urban environment by, for example, reducing heat island effects, promoting better air quality, and protecting local habitat. The majority of efforts to expand canopy cover focus on planting street trees or on planting native tree species and removing nonnatives in natural areas through reforestation. Yet many urban canopy assessments conducted at the city-scale reveal co-dominance by nonnative trees, fueling debates about the value of urban forests and native-specific management targets. In contrast, assessments within cities at site or park scales find that some urban forest stands harbor predominantly native biodiversity. To resolve this apparent dichotomy in findings, about the extent to which urban forests are native dominated, between the city-scale canopy and site-level assessments, we measure forest structure and composition in 1,124 plots across 53 parks in New York City's 2,497 ha of natural area forest. That is, we assess urban forests at the city-scale and deliberately omit sampling trees existing outside of forest stands but which are enumerated in citywide canopy assessments. We find that on average forest stand canopy is comprised of 82% native species in New York City forests, suggesting that conclusions that the urban canopy is co-dominated by nonnatives likely results from predominantly sampling street trees in prior city-scale assessments. However, native tree species' proportion declines to 75% and 53% in the midstory and understory, respectively, suggesting potential threats to the future native dominance of urban forest canopies. Furthermore, we find that out of 57 unique forest types in New York City, the majority of stands (81%) are a native type. We find that stand structure in urban forest stands is more similar to rural forests in New York State than to stand structure reported for prior assessments of the urban canopy at the city scale. Our results suggest the need to measure urban forest stands apart from the entire urban canopy. Doing so will ensure that city-scale assessments return data that align with conservation policy and management strategies that focus on maintaining and growing native urban forests rather than individual trees.