Increased efforts are required to prevent further losses to terrestrial biodiversity and the ecosystem services that it provides
. Ambitious targets have been proposed, such as reversing the ...declining trends in biodiversity
; however, just feeding the growing human population will make this a challenge
. Here we use an ensemble of land-use and biodiversity models to assess whether-and how-humanity can reverse the declines in terrestrial biodiversity caused by habitat conversion, which is a major threat to biodiversity
. We show that immediate efforts, consistent with the broader sustainability agenda but of unprecedented ambition and coordination, could enable the provision of food for the growing human population while reversing the global terrestrial biodiversity trends caused by habitat conversion. If we decide to increase the extent of land under conservation management, restore degraded land and generalize landscape-level conservation planning, biodiversity trends from habitat conversion could become positive by the mid-twenty-first century on average across models (confidence interval, 2042-2061), but this was not the case for all models. Food prices could increase and, on average across models, almost half (confidence interval, 34-50%) of the future biodiversity losses could not be avoided. However, additionally tackling the drivers of land-use change could avoid conflict with affordable food provision and reduces the environmental effects of the food-provision system. Through further sustainable intensification and trade, reduced food waste and more plant-based human diets, more than two thirds of future biodiversity losses are avoided and the biodiversity trends from habitat conversion are reversed by 2050 for almost all of the models. Although limiting further loss will remain challenging in several biodiversity-rich regions, and other threats-such as climate change-must be addressed to truly reverse the declines in biodiversity, our results show that ambitious conservation efforts and food system transformation are central to an effective post-2020 biodiversity strategy.
Biodiversity and ecosystem service losses driven by land-use change are expected to intensify as a growing and more affluent global population requires more agricultural and forestry products, and ...teleconnections in the global economy lead to increasing remote environmental responsibility. By combining global biophysical and economic models, we show that, between the years 2000 and 2011, overall population and economic growth resulted in increasing total impacts on bird diversity and carbon sequestration globally, despite a reduction of land-use impacts per unit of gross domestic product (GDP). The exceptions were North America and Western Europe, where there was a reduction of forestry and agriculture impacts on nature accentuated by the 2007-2008 financial crisis. Biodiversity losses occurred predominantly in Central and Southern America, Africa and Asia with international trade an important and growing driver. In 2011, 33% of Central and Southern America and 26% of Africa's biodiversity impacts were driven by consumption in other world regions. Overall, cattle farming is the major driver of biodiversity loss, but oil seed production showed the largest increases in biodiversity impacts. Forestry activities exerted the highest impact on carbon sequestration, and also showed the largest increase in the 2000-2011 period. Our results suggest that to address the biodiversity crisis, governments should take an equitable approach recognizing remote responsibility, and promote a shift of economic development towards activities with low biodiversity impacts.
Land use and hunting are 2 major pressures on biodiversity in the tropics. Yet, their combined impacts have not been systematically quantified at a large scale. We estimated the effects of both ...pressures on the distributions of 1884 tropical mammal species by integrating species’ range maps, detailed land‐use maps (1992 and 2015), species‐specific habitat preference data, and a hunting pressure model. We further identified areas where the combined impacts were greatest (hotspots) and least (coolspots) to determine priority areas for mitigation or prevention of the pressures. Land use was the main driver of reduced distribution of all mammal species considered. Yet, hunting pressure caused additional reductions in large‐bodied species’ distributions. Together, land use and hunting reduced distributions of species by 41% (SD 30) on average (year 2015). Overlap between impacts was only 2% on average. Land use contributed more to the loss of distribution (39% on average) than hunting (4% on average). However, hunting reduced the distribution of large mammals by 29% on average; hence, large mammals lost a disproportional amount of area due to the combination of both pressures. Gran Chaco, the Atlantic Forest, and Thailand had high levels of impact across the species (hotspots of area loss). In contrast, the Amazon and Congo Basins, the Guianas, and Borneo had relatively low levels of impact (coolspots of area loss). Overall, hunting pressure and human land use increased from 1992 to 2015 and corresponding losses in distribution increased from 38% to 41% on average across the species. To effectively protect tropical mammals, conservation policies should address both pressures simultaneously because their effects are highly complementary. Our spatially detailed and species‐specific results may support future national and global conservation agendas, including the design of post‐2020 protected area targets and strategies.
Efectos Combinados del Uso de Suelo y la Caza en la Distribución de los Mamíferos Tropicales
Resumen
El uso de suelo y la caza son dos de las principales presiones ejercidas sobre la biodiversidad de los trópicos. Aun así, los impactos combinados que generan no han sido cuantificados sistemáticamente a gran escala. Estimamos los efectos de ambas presiones sobre la distribución de 1,884 especies de mamíferos tropicales al integrar mapas de distribución de las especies, mapas detallados del uso de suelo (de 1992 y 2015), datos de preferencia de hábitat específicos por especie y un modelo de presión de caza. Identificamos además las áreas en donde los impactos combinados eran mayores (puntos calientes) y menores (puntos fríos) para determinar las áreas prioritarias para la mitigación o prevención de dichas presiones. El uso de suelo fue el principal conductor de la reducción de la distribución para todas las especies de mamíferos que consideramos. Sin embargo, la presión por caza causó reducciones adicionales en la distribución de especies de gran tamaño. Juntas, el uso de suelo y la caza redujeron la distribución de las especies en un 41% (DS 30) en promedio (año 2015). El solapamiento entre los impactos fue, en promedio, sólo del 2%. El uso de suelo contribuyó más a la pérdida de la distribución (39%, en promedio) que la caza (4%, en promedio). A pesar de esto, en promedio la caza redujo la distribución de los mamíferos de gran tamaño en un 29%; por lo tanto, los grandes mamíferos perdieron una cantidad desproporcionada de área debido a la combinación de ambas presiones. El Gran Chaco, el Bosque Atlántico y Tailandia tuvieron niveles altos de impacto en todas las especies (puntos calientes de pérdida de área). Como contraste, las cuencas del Amazonas y el Congo, las Guayanas y Borneo tuvieron niveles relativamente bajos de impacto (puntos fríos de pérdida de área). En general, las presiones por caza y uso de suelo incrementaron desde 1992 a 2015 y las correspondientes pérdidas de distribución incrementaron de un 38% a un 41% en promedio para todas las especies. Para proteger de forma efectiva a los mamíferos tropicales, las políticas de conservación deberían considerar a ambas presiones de manera simultánea, pues sus efectos son altamente complementarios. Nuestros resultados espacialmente detallados y específicos para cada especie pueden respaldar las futuras agendas de conservación nacionales e internacionales, incluyendo el diseño de las estrategias y los objetivos de las áreas protegidas para después de 2020.
摘要
土地利用和狩猎是热带地区生物多样性面临的两大压力。然而, 它们的共同影响尚未在大尺度上得到系统的定量研究。我们通过整合物种分布范围、详细的土地利用地图 (1992 年及 2015 年) 、物种特异的栖息地偏好数据和狩猎压力模型, 估计了这两种压力对 1884 种热带哺乳动物分布的影响。我们进一步确定了二者共同影响最强 (热点) 和最弱 (冷点) 的地区, 以确定减缓或预防压力的优先区域。土地利用是所有哺乳动物分布减少的主要原因, 而狩猎压力则导致大型动物的分布范围进一步缩小。土地利用和狩猎使物种分布范围平均减少了 41% (标准差 30) (2015 年) 。而两种压力的影响平均只有 2% 的重叠范围。土地利用对物种分布减少的作用 (平均 39%) 大于狩猎 (平均 4%) 。然而, 狩猎使大型哺乳动物的分布平均减少了 29%; 因此, 大型哺乳动物在这两种压力的共同作用下分布区不成比例地发生退缩。格兰查科、大西洋森林和泰国为分布区缩小的热点地区, 对所有哺乳动物都有很大的影响。而亚马逊和刚果盆地、圭亚那及婆罗洲是影响相对较弱的地区。总的来说, 1992 年至 2015 年来, 狩猎压力和人类土地利用压力都越来越严重, 所有物种平均的分布区丧失也从 38% 增加到 41% 。为了有效地保护热带哺乳动物, 保护政策需同时应对这两种压力, 因为它们的作用是高度互补的。我们富有空间细节和物种特异性的研究结果可以支持未来的国家及全球保护议程, 包括 2020 年后保护地目标和战略的设计。【翻译: 胡怡思; 审校: 聂永刚】
Article impact statement: Tropical mammals have lost on average 40% of their original distribution due to the combined effect of hunting pressure and human land use.
Scenario‐based biodiversity modelling is a powerful approach to evaluate how possible future socio‐economic developments may affect biodiversity. Here, we evaluated the changes in terrestrial ...biodiversity intactness, expressed by the mean species abundance (MSA) metric, resulting from three of the shared socio‐economic pathways (SSPs) combined with different levels of climate change (according to representative concentration pathways RCPs): a future oriented towards sustainability (SSP1xRCP2.6), a future determined by a politically divided world (SSP3xRCP6.0) and a future with continued global dependency on fossil fuels (SSP5xRCP8.5). To this end, we first updated the GLOBIO model, which now runs at a spatial resolution of 10 arc‐seconds (~300 m), contains new modules for downscaling land use and for quantifying impacts of hunting in the tropics, and updated modules to quantify impacts of climate change, land use, habitat fragmentation and nitrogen pollution. We then used the updated model to project terrestrial biodiversity intactness from 2015 to 2050 as a function of land use and climate changes corresponding with the selected scenarios. We estimated a global area‐weighted mean MSA of 0.56 for 2015. Biodiversity intactness declined in all three scenarios, yet the decline was smaller in the sustainability scenario (−0.02) than the regional rivalry and fossil‐fuelled development scenarios (−0.06 and −0.05 respectively). We further found considerable variation in projected biodiversity change among different world regions, with large future losses particularly for sub‐Saharan Africa. In some scenario‐region combinations, we projected future biodiversity recovery due to reduced demands for agricultural land, yet this recovery was counteracted by increased impacts of other pressures (notably climate change and road disturbance). Effective measures to halt or reverse the decline of terrestrial biodiversity should not only reduce land demand (e.g. by increasing agricultural productivity and dietary changes) but also focus on reducing or mitigating the impacts of other pressures.
We project the changes in terrestrial biodiversity intactness from 2015 to 2050 corresponding with three of the shared socio‐economic pathways combined with different levels of climate change, using an updated version of the GLOBIO model. Biodiversity intactness declined in all three scenarios, with large losses particularly for sub‐Saharan Africa. Effective measures to halt or reverse the decline of terrestrial biodiversity should not only reduce land demand but also reduce or mitigate the impacts of other pressures.
The IUCN (International Union for Conservation of Nature) Red List categories and criteria are the most widely used framework for assessing the relative extinction risk of species. The criteria are ...based on quantitative thresholds relating to the size, trends, and structure of species’ distributions and populations. However, data on these parameters are sparse and uncertain for many species and unavailable for others, potentially leading to their misclassification or classification as data deficient. We devised an approach that combines data on land‐cover change, species‐specific habitat preferences, population abundance, and dispersal distance to estimate key parameters (extent of occurrence, maximum area of occupancy, population size and trend, and degree of fragmentation) and hence predict IUCN Red List categories for species. We applied our approach to nonpelagic birds and terrestrial mammals globally (∼15,000 species). The predicted categories were fairly consistent with published IUCN Red List assessments, but more optimistic overall. We predicted 4.2% of species (467 birds and 143 mammals) to be more threatened than currently assessed and 20.2% of data deficient species (10 birds and 114 mammals) to be at risk of extinction. Incorporating the habitat fragmentation subcriterion reduced these predictions 1.5–2.3% and 6.4–14.9% (depending on the quantitative definition of fragmentation) for threatened and data deficient species, respectively, highlighting the need for improved guidance for IUCN Red List assessors on the application of this aspect of the IUCN Red List criteria. Our approach complements traditional methods of estimating parameters for IUCN Red List assessments. Furthermore, it readily provides an early‐warning system to identify species potentially warranting changes in their extinction‐risk category based on periodic updates of land‐cover information. Given our method relies on optimistic assumptions about species distribution and abundance, all species predicted to be more at risk than currently evaluated should be prioritized for reassessment.
Aplicación de Modelos de Hábitat y de Densidad Poblacional a Series de Tiempo de la Cobertura del Suelo para Informar las Valoraciones de la Lista Roja de la UICN
Resumen
Las categorías y los criterios de la Lista Roja de la UICN (Unión Internacional para la Conservación de la Naturaleza) son el marco de referencia utilizado con mayor frecuencia para valorar el riesgo de extinción relativo de las especies. Los criterios se basan en umbrales cuantitativos relacionados con el tamaño, las tendencias y la estructura de la distribución y las poblaciones de las especies. Sin embargo, los datos sobre estos parámetros son escasos e inciertos para muchas especies y para otras no se encuentran disponibles, lo puede resultar en una clasificación errónea o en que se las clasifique como una especie con deficiencia de datos. Hemos diseñado una estrategia que combina datos sobre el cambio en la cobertura del suelo, las preferencias de hábitat específicas por especie, la abundancia poblacional, y la distancia de dispersión para estimar los parámetros más importantes (extensión de la presencia, área máxima de ocupación, tamaño poblacional, y grado y tendencia de la fragmentación) y así predecir las categorías de la Lista Roja de la UICN para cada especie. Hemos aplicado nuestra estrategia a las aves no pelágicas y a los mamíferos terrestres de todo el mundo (∼15,000 especies). Las categorías pronosticadas fueron bastante consecuentes con las valoraciones publicadas por la Lista Roja de la UICN, aunque en general fueron más optimistas. Pronosticamos que el 4.2% de las especies (467 aves y 143 mamíferos) se encuentran más amenazadas que su valoración actual y el 20.2% de las especies con deficiencia de datos (10 aves y 114 mamíferos) se encuentran en riesgo de extinción. La incorporación del sub‐criterio de fragmentación del hábitat redujo estas predicciones en un 1.5 – 2.3% y 6.4 – 14.9% (dependiendo de la definición cuantitativa de la fragmentación) para las especies amenazadas y las que tienen deficiencia de datos, respectivamente, lo que resalta la necesidad de mejorar la aplicación de este sub‐criterio por parte de los asesores de la Lista Roja de la UICN. Nuestra estrategia complementa los métodos tradicionales de estimación de parámetros para las valoraciones de la Lista Roja. Además, proporciona un sistema inmediato de alerta temprana basado en actualizaciones periódicas de la información sobre la cobertura del suelo que permite identificar a las especies que, potencialmente, merezcan un cambio en su categoría de riesgo de extinción. Nuestro método está basado en suposiciones optimistas sobre la distribución y la abundancia de las especies, por lo tanto todas las especies que predecimos que tienen una mayor categoría de riesgo que la que reconoce la evaluación actual deberían ser priorizadas para su revaloración.
摘要
世界自然保护联盟 (International Union for Conservation of Nature, IUCN) 红色名录濒危等级和评估标准是物种相对灭绝风险评估中应用得最为广泛的一套框架。这些标准的制定依据与物种分布和种群的大小、趋势和结构有关的定量阈值。然而, 许多物种这些参数的数据稀缺、具有不确定性, 甚至一些物种的数据难以获得和利用, 这可能导致它们被错误地划分濒危等级, 或被归类为“数据缺乏”。我们设计了一种方法, 结合土地覆盖变化、物种特异的生境偏好、种群丰度和扩散距离的数据, 来估计物种的关键参数 (出现范围、最大占有面积、种群大小和趋势、破碎化程度), 从而预测它们的 IUCN 红色名录濒危等级。我们应用这个方法预测了全球非远洋鸟类和陆地哺乳动物 (约 15,000 种) 的濒危等级。预测的濒危等级与 IUCN 红色名录评估结果基本一致, 但总体上更为乐观。预测结果中, 4.2% 的物种 (467 种鸟类和 143 种哺乳动物) 比目前的评估情况更濒危, 且数据缺乏的物种中 20.2% (10 种鸟类和 114 种哺乳动物) 面临灭绝风险。进一步整合生境破碎化的子标准后, 受胁迫物种及数据缺乏物种分别减少了 1.5‐2.3% 和 6.4‐14.9% (取决于对破碎化的定量标准), 这强调了需要更好地指导 IUCN 红色名录评估者对评估标准中相关指标的应用。我们的方法是对红色名录评估中传统的参数估计方法的补充。此外, 它还提供了一个早期预警系统, 可以基于定期更新的土地覆盖数据, 来确定濒危等级可能发生变化的物种。鉴于这一方法依赖于对物种分布和丰度的乐观假设, 所有在预测中比目前评估的濒危风险更大的物种都应该优先进行重新评估。 【翻译: 胡怡思; 审校: 聂永刚】
Article impact statement: Automatic screening to prioritize species reassessments optimizes the use of resources and keeps the IUCN Red List up to date.
New Guinea is one of the last regions in the world with vast pristine areas and is home to many endemic species. However, extensive road development plans threaten the island's biodiversity. We ...quantified habitat fragmentation due to existing and planned roads for 139 terrestrial mammal species in New Guinea. For each species, we calculated the equivalent connected area (ECA) of habitat, a metric that takes into account the area and connectivity of habitat patches in 3 situations: no roads (baseline situation), existing roads (current), and existing and planned roads combined (future). We assessed the effect of roads as the proportion of the ECA remaining in the current and future situations relative to the baseline. To examine whether there were patterns in these relative ECA values, we fitted beta‐regression models relating these values to 4 species characteristics: taxonomic order, body mass, diet, and International Union for the Conservation of Nature Red List status. On average across species, current ECA was 89% (SD 12) of baseline ECA. Shawmayer's coccymys (Coccymys shawmayeri) had the lowest amount of current ECA relative to the baseline (53%). In the future situation, the average remaining ECA was 71% (SD 20) of baseline ECA. Future remaining ECA was below 50% of the baseline for 28 species. The montane soft‐furred paramelomys (Paramelomys mollis) had the lowest future ECA relative to the baseline (36%). In general, currently nonthreatened carnivorous species with a large body mass had the greatest reductions of ECA in the future situation. In conclusion, future road development plans imply extensive additional habitat fragmentation for a large number of terrestrial mammal species in New Guinea. It is therefore important to limit the impact of planned roads, for example, by reconsidering the location of planned roads that intersect habitat of the most threatened species, or by the implementation of mitigation measures such as underpasses.
Impacto de las carreteras planeadas y existentes sobre el hábitat de mamíferos terrestres en Nueva Guinea
Resumen
Nueva Guinea es una de las últimas regiones del mundo con zonas vírgenes extensas que alberga muchas especies endémicas. Sin embargo, los planes extensivos de desarrollo de carreteras amenazan la biodiversidad de la isla. Cuantificamos la fragmentación del hábitat causada por las carreteras existentes y previstas para 139 especies de mamíferos terrestres de Nueva Guinea. Para cada especie, calculamos el área conectada equivalente (ACE) del hábitat, una medida que considera el área y la conectividad de los fragmentos de hábitat en tres situaciones: sin carreteras (situación de referencia), carreteras existentes (actual) y la combinación de carreteras existentes y previstas (futuro). Evaluamos el efecto de las carreteras como la proporción de ACE que quedaba en las situaciones actual y futura en relación con la situación de referencia. Para examinar si existían patrones en estos valores relativos de ECA, ajustamos modelos de regresión beta relacionando estos valores con cuatro características de las especies: orden taxonómico, masa corporal, dieta y estado en la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza. En promedio para todas las especies, la ACE actual fue 89% (DE 12) de la ACE basal. La especie Coccymys shawmayeri presentó la menor cantidad de ACE actual en relación con la base de referencia (53%). En la situación futura, la media de ACE restante fue del 71% (DE 20) de la ACE de referencia. La ACE restante futura fue inferior al 50% de la línea de base para 28 especies. La especie Paramelomys mollis tuvo la ACE futura más baja en relación con la línea base (36%). En general, las especies carnívoras que no están amenazadas actualmente y tienen una masa corporal grande tuvieron la mayor reducción de ACE en la situación futura. Para concluir, la futura construcción de carreteras implica una extensa fragmentación de hábitat adicional para un gran número de especies de mamíferos terrestres en Nueva Guinea. Por esto es importante limitar el impacto de las carreteras planeadas, por ejemplo, reconsiderando la ubicación de las carreteras que cruzan el hábitat de las especies más amenazadas o implementando medidas de mitigación como los pasos subterráneos.
As animal home range size (HRS) provides valuable information for species conservation, it is important to understand the driving factors of HRS variation. It is widely known that differences in ...species traits (e.g. body mass) are major contributors to variation in mammal HRS. However, most studies examining how environmental variation explains mammal HRS variation have been limited to a few species, or only included a single (mean) HRS estimate for the majority of species, neglecting intraspecific HRS variation. Additionally, most studies examining environmental drivers of HRS variation included only terrestrial species, neglecting marine species. Using a novel dataset of 2800 HRS estimates from 586 terrestrial and 27 marine mammal species, we quantified the relationships between HRS and environmental variables, accounting for species traits. Our results indicate that terrestrial mammal HRS was on average 5.3 times larger in areas with low human disturbance (human footprint index HFI = 0), compared to areas with maximum human disturbance (HFI = 50). Similarly, HRS was on average 5.4 times larger in areas with low annual mean productivity (NDVI = 0), compared to areas with high productivity (NDVI = 1). In addition, HRS increased by a factor of 1.9 on average from low to high seasonality in productivity (standard deviation (SD) of monthly NDVI from 0 to 0.36). Of these environmental variables, human disturbance and annual mean productivity explained a larger proportion of HRS variance than seasonality in productivity. Marine mammal HRS decreased, on average, by a factor of 3.7 per 10°C decline in annual mean sea surface temperature (SST), and increased by a factor of 1.5 per 1°C increase in SST seasonality (SD of monthly values). Annual mean SST explained more variance in HRS than SST seasonality. Due to the small sample size, caution should be taken when interpreting the marine mammal results. Our results indicate that environmental variation is relevant for HRS and that future environmental changes might alter the HRS of individuals, with potential consequences for ecosystem functioning and the effectiveness of conservation actions.
In conservation decision‐making, it is important to have information not only on the likely effectiveness of conservation actions, but also on the corresponding costs. Reintroduction of wildlife is a ...commonly applied ‘last resort’ conservation measure. However, a quantitative approach to predict the costs of reintroduction for sustaining a wildlife population under the influence of time‐varying anthropogenic stress is lacking.
Here, we fill this gap by quantifying the costs of reintroduction as a function of exposure to an environmental stressor and the size of the wildlife population to be maintained. Our approach combines quantitative stressor–response relationships for vital rates (reproduction and survival) with a wildlife demographic model to compute the impacts of the stressor on the size of the target population. Subsequently, cost estimates are obtained by quantifying the number of captive‐reared individuals needed per year in order to maintain a user‐defined population size, given the exposure to the stressor of concern. We applied our approach to calculate the reintroduction costs required to restore a minimum viable population (MVP) of peregrine falcons (Falco peregrinus) in California over the period 1970–1994, when the population was exposed to the toxicant dichlorodiphenyldichloroethylene.
Assuming a gradual yearly increase of 150% in the availability of captive‐reared young, 1,753 captive‐reared young were required to restore and maintain a MVP of 238 adults. The corresponding reintroduction costs were in total ~$3,023,000. Assuming lower reintroduction efforts (in terms of the availability of captive‐reared young), the projected reintroduction costs decreased by ~33%. However, the population then reached the minimum viable size only 9 years later, thus reflecting a trade‐off between costs and population viability.
Synthesis and applications. The approach presented in this study ensures an adequate prediction of the costs of maintaining a wildlife population at a user‐defined size through reintroduction. It can be applied to any wildlife population in order to obtain the number of individuals and corresponding costs required to sustain a population under current and future influence of an anthropogenic stressor. This type of information provides important input for decision‐making necessary to conserve biodiversity.
The approach presented in this study ensures an adequate prediction of the costs of maintaining a wildlife population at a user‐defined size through reintroduction. It can be applied to any wildlife population in order to obtain the number of individuals and corresponding costs required to sustain a population under current and future influence of an anthropogenic stressor. This type of information provides important input for decision‐making necessary to conserve biodiversity.
Biodiversity is severely threatened by habitat destruction. As a consequence of habitat destruction, the remaining habitat becomes more fragmented. This results in time‐lagged population extirpations ...in remaining fragments when these are too small to support populations in the long term. If these time‐lagged effects are ignored, the long‐term impacts of habitat loss and fragmentation will be underestimated. We quantified the magnitude of time‐lagged effects of habitat fragmentation for 157 nonvolant terrestrial mammal species in Madagascar, one of the biodiversity hotspots with the highest rates of habitat loss and fragmentation. We refined species’ geographic ranges based on habitat preferences and elevation limits and then estimated which habitat fragments were too small to support a population for at least 100 years given stochastic population fluctuations. We also evaluated whether time‐lagged effects would change the threat status of species according to the International Union for the Conservation of Nature (IUCN) Red List assessment framework. We used allometric relationships to obtain the population parameters required to simulate the population dynamics of each species, and we quantified the consequences of uncertainty in these parameter estimates by repeating the analyses with a range of plausible parameter values. Based on the median outcomes, we found that for 34 species (22% of the 157 species) at least 10% of their current habitat contained unviable populations. Eight species (5%) had a higher threat status when accounting for time‐lagged effects. Based on 0.95‐quantile values, following a precautionary principle, for 108 species (69%) at least 10% of their habitat contained unviable populations, and 51 species (32%) had a higher threat status. Our results highlight the need to preserve continuous habitat and improve connectivity between habitat fragments. Moreover, our findings may help to identify species for which time‐lagged effects are most severe and which may thus benefit the most from conservation actions.
Resumen
La biodiversidad se encuentra seriamente amenazada por la destrucción del hábitat. Como consecuencia de esta destrucción, el hábitat remanente se vuelve más fragmentado. Esto resulta en extirpaciones poblacionales retardadas dentro de los fragmentos restantes cuando éstos son muy pequeños para mantener a las poblaciones a largo plazo. Si se ignoran estos efectos retardados, se subestimarán los impactos a largo plazo de la pérdida del hábitat y la fragmentación. Cuantificamos la magnitud de los efectos retardados de la fragmentación del hábitat para 157 especies de mamíferos terrestres no voladores en Madagascar, uno de los puntos calientes de biodiversidad con las tasas más elevadas de pérdida del hábitat y fragmentación. Depuramos las extensiones geográficas de las especies con base en las preferencias de hábitat y los límites de elevación y después estimamos cuáles fragmentos de hábitat eran muy pequeños para mantener una población durante al menos cien años dadas las fluctuaciones estocásticas de las poblaciones. También analizamos si los efectos retardados cambiarían el estado de amenaza de la especie de acuerdo con el programa de evaluación de la Lista Roja de la UICN. Usamos relaciones alométricas para obtener los parámetros poblacionales requeridos para simular las dinámicas poblacionales de cada especie y cuantificamos las consecuencias de la incertidumbre en estos parámetros estimados mediante análisis repetidos con una gama de valores plausibles de los parámetros. Con base en los resultados promedio, descubrimos que para 34 especies (22% de las 157 especies) al menos el 10% de su hábitat actual tiene poblaciones inviables. Ocho especies (5%) cambiaron a un estado más elevado de amenaza cuando se consideraron los efectos retardados. Con base en los valores del centil 0.95, adherido a un principio precautorio, para 108 especies (32%) al menos el 10% de su hábitat tiene poblaciones inviables y 51 especies (32%) cambiaron negativamente su estado de amenaza. Nuestros resultados resaltan la necesidad de conservar la continuidad de los hábitats y mejorar la conectividad entre los fragmentos. Además, nuestros hallazgos pueden ayudar a identificar especies para las cuales los efectos retardados son más serios y que podrían beneficiarse más con las acciones de conservación.
【摘要】
生物多样性面临着栖息地破坏的严重威胁。栖息地破坏会导致剩余的栖息地破碎化更加严重, 进而在剩余破碎化栖息地的面积不足以长期支持种群发展时, 引发时间滞后的种群灭绝。如果忽视这种时滞效应, 那么将会低估栖息地丧失和破碎化的长期影响。马达加斯加是栖息地丧失和破碎化比例最高的生物多样性热点地区之一, 本研究量化了马达加斯加157种非飞行陆地哺乳动物栖息地破碎化的时滞效应。我们根据物种的栖息地偏好和海拔限制精细划分了其地理范围, 并估计在随机种群波动下, 哪些破碎化栖息地的面积不足以支持种群存活至少100年。我们还根据《世界自然保护联盟红色名录》的评估框架, 评估了时滞效应是否会改变物种的濒危等级。我们使用异速关系得到了每个物种种群动态模拟所需的种群参数, 并通过对一系列合理的参数值进行重复分析, 量化了这些参数估计的不确定性结果。我们发现基于中位数的结果, 有34个物种 (在157个物种中占22%) 当前的栖息地中至少有10% 包含难以存活的种群。如果考虑到时滞效应, 8个物种 (5%) 应被纳入更高的濒危等级。而基于0.95分位数的结果, 则有 108个物种 (69%) 在预防性原则下至少有10% 的栖息地包含难以存活的种群, 51个物种 (32%) 会被纳入更高的濒危等级。我们的结果强调了保护连续栖息地和提高破碎化栖息地连接度的必要性。此外, 我们的研究结果还有助于确定受时滞效应影响最严重且将从保护行动中受益最大的物种。【翻译: 胡怡思; 审校: 聂永刚】
Abstract
Land use is a major cause of biodiversity decline worldwide. Agricultural and forestry diversification measures, such as the inclusion of natural elements or diversified crop types, may ...reduce impacts on biodiversity. However, the extent to which such measures may compensate for the negative impacts of land use remains unknown. To fill that gap, we synthesised data from 99 studies that recorded mammal populations or assemblages in natural reference sites and in cropland and forest plantations, with or without diversification measures. We quantified the responses to diversification measures based on individual species abundance, species richness and assemblage intactness as quantified by the mean species abundance indicator. In cropland with natural elements, mammal species abundance and richness were, on average, similar to natural conditions, while in cropland without natural elements they were reduced by 28% and 34%, respectively. We found that mammal species richness was comparable between diversified forest plantations and natural reference sites, and 32% lower in plantations without natural elements. In both cropland and plantations, assemblage intactness was reduced compared with natural reference conditions, but the reduction was smaller if diversification measures were in place. In addition, we found that responses to land use were modified by species traits and environmental context. While habitat specialist populations were reduced in cropland without diversification and in forest plantations, habitat generalists benefited. Furthermore, assemblages were impacted more by land use in tropical regions and landscapes containing a larger share of (semi)natural habitat compared with temperate regions and more converted landscapes. Given that mammal assemblage intactness is reduced also when diversification measures are in place, special attention should be directed to species that suffer from land use impacts. That said, our results suggest potential for reconciling land use and mammal conservation, provided that the diversification measures do not compromise yield.
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