Human population growth and economic development threaten the integrity of freshwater ecosystems globally, reducing their ability to support biodiversity and provide ecosystem services. However, our knowledge of freshwater biodiversity is fragmented due to bias in conservation research toward primarily terrestrial or charismatic taxonomic groups. Here, we utilize the most comprehensive assessment of freshwater biodiversity for an entire continent to examine the implications of this shortfall. Results indicate that groups that have been the focus of most conservation research are poor surrogates for patterns of both richness and threat for many freshwater groups, and that the existing protected area network underrepresents freshwater species. Areas of highest species richness and threat are congruent with areas where reliance on ecosystem services by humans and pressures placed on freshwater ecosystems are high. These results have implications for targets to reduce biodiversity loss and safeguard associated ecosystem services on which millions of people depend globally.
We discuss the probability distribution function (PDF) of column density resulting from density fields with lognormal PDFs, applicable to molecular clouds. For magnetic and non-magnetic numerical simulations of compressible, isothermal turbulence, we show that the autocorrelation function (ACF) of the density field decays over short distances compared to the simulation size. A "correlation length" can be defined as the distance over which the density ACF has decayed to, for example, 10% of its zero-lag value. The density "events" along a line of sight can thus be assumed to be independent over distances larger than this, and the Central Limit Theorem should be applicable. However, using random realizations of lognormal fields, we show that the convergence to a Gaussian is extremely slow in the high-density tail. As a consequence, the column density PDF is not expected to exhibit a unique functional shape, but to transit instead from a lognormal to a Gaussian form as the column length increases, and with decreasing variance. For intermediate path lengths, the column density PDF assumes a nearly exponential decay. For cases with a density contrast of 10 4 (resp. 10 6), as found in intermediate-resolution simulations, and expected from GMCs to dense molecular cores, the required length for convergence is at least a few hundred (resp. several thousand) independent events. Therefore, we suggest that all 3D MHD simulations to date are insufficiently resolved for obtaining a reasonably converged Gaussian PDF for the column density. Observationally, our results imply that the column length (in units of the correlation length) may be inferred from the shape of the column density PDF in optically-thin-line or extinction studies: as the path length increases, the PDF is expected to undergo the shape sequence mentioned above. A similar behavior is expected for underlying density PDFs with finite-extent power-law ranges, which should be characteristic of lower density, non-isothermal gas (with temperatures ranging from a few hundred to a few thousand degrees). Finally, we note that for long path lengths (over a few hundred independent events), the dynamic range in column density is small (∼ < a factor of 10), but this is only an averaging effect, with no implication on the dynamic range of the underlying density distribution.
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About IUCNIUCN, International Union for Conservation of Nature, helps the world find pragmatic solutions to our most pressing environment and development challenges.IUCN's work focuses on valuing and conserving nature, ensuring effective and equitable governance of its use, and deploying nature-based solutions to global challenges in climate, food and development. IUCN supports scientific research, manages field projects all over the world, and brings governments, NGOs, the UN and companies together to develop policy, laws and best practice.IUCN is the world's oldest and largest global environmental organization, with more than 1,200 government and NGO Members and almost 11,000 volunteer experts in some 160 countries. IUCN's work is supported by over 1,000 staff in 45 offices and hundreds of partners in public, NGO and private sectors around the world. About the Species Survival CommissionThe Species Survival Commission (SSC) is the largest of IUCN's six volunteer commissions with a global membership of around 7,500 experts. SSC advises IUCN and its members on the wide range of technical and scientific aspects of species conservation, and is dedicated to securing a future for biodiversity. SSC has significant input into the international agreements dealing with biodiversity conservation. About Conservation InternationalBuilding upon a strong foundation of science, partnership and field demonstration, Conservation International (CI) empowers societies to responsibly and sustainably care for nature and its global biodiversity to promote the long-term well-being of people. Founded in 1987 and marking its 25th anniversary in 2012, CI is head quartered in the Washington, D.C. area. CI employs 900 staff in more than 25 countries on four continents and works with more than 1,000 partners around the world. About the Environment Agency -Abu DhabiThe Environment Agency -Abu Dhabi (EAD) is a governmental agency that was established in 1996 with the overall function of protecting and conserving the environment as well as promoting sustainable development in the Emirate of Abu Dhabi, the capital of the United Arab Emirates (UAE). The Agency is responsible for assisting the UAE Ministry of Environment and Water in implementing environmental laws and putting forth regulation orders in the capital.The IUCN Species Survival Commission and the IUCN Global Species Programme have enjoyed a close working relationship with Abu Dhabi for the last 20 years particularly on issues such as species conservation and re-introduction as well as Red List assessment and training. EAD has been a long-time supporter of the SSC Re-introduction Specialist Group and hosted the meeting of the SSC Specialist Group Chairs in 2008 and 2012. THE STATUS AND DISTRIBUTION OF FRESHWATER BIODIVERSITY IN THE ARABIAN PENINSULACompiled by Nieves García, Ian Harrison, Neil Cox and Marcelo F. TognelliThe designation of geographical entities in this book, and the presentation of the material, do not imply the expression of any opinion whatsoever on the part of IUCN...
El estudio de los impactos ecológicos de la fragmentación y la pérdida de hábitat es importante para la conservación de la diversidad1. Una propiedad de las biotas en ecosistemas fragmentados es el anidamiento: especies presentes en áreas de baja riqueza son muestras de las presentes en las de mayor riqueza2. La evaluación del anidamiento ha sido utilizada para predecir el grado al cual la fragmentación produce cambios en riqueza de especies en una secuencia predecible3-5 . Sin embargo, no se han realizado muchas evaluaciones de esta propiedad en el neotrópico, particularmente en hábitats urbanos. En este trabajo se evaluó el anidamiento de aves entre zonas verdes de un hábitat urbano, realizando censos visuales de aves en áreas de diferentes tamaños y grados de aislamiento en la ciudad de Cali. Para evaluar el grado de anidamiento, total y gremial, se comparó el índice NODF del ensamblaje contra el generado a partir de modelos nulos. El ensamblaje total presentó una distribución anidada significativa; sin embargo, a nivel de gremios, sólo las aves frugívoras exhibieron anidamiento significativo. La organización decreciente de máximo anidamiento de las zonas verdes mostró una relación negativa con el área y positiva con el aislamiento, lo cual sugiere que las diferencias entre las zonas verdes fueron debidas a extinción y colonización; respectivamente. En conclusión, aunque el ensamblaje de aves exhibió anidamiento, el patrón de recambio de especies fue diferente entre los gremios, por lo tanto, los sitios con pocas especies contribuyen a la biodiversidad a escala del paisaje; particularmente para especies insectívoras, nectarívoras y omnívoras. Adicionalmente, las aves frugívoras presentaron mayor anidamiento que las de otros gremios, lo cual implica que la pérdida secuencial de especies es más predecible en este grupo; y que el proceso de fragmentación afecta la organización trófica de las comunidades.Cómo citar este resumen: Murillo-García, O. E., Mora-Medina, L. C., Castillo, S., Castillo, M. A., García, A., Sánchez-Sarria, C., Vargas-Rivera, G., García, M. C., Perlaza, A., Vargas-Garcia, N., Triana, C., López-Díaz, E., Torres, G., Murillo, Y., Estupiñan, D. L., Altuwaee-Alejo, M., Molano, J., Aguirre, G. K. and Barreiro, M, Impactos Ecológicos De La Fragmentación: Patrones De Anidamiento De Aves En Zonas Verdes De Un Hábitat Urbano. Innovaciencia facultad cienc. exactas fis. naturales. 2017; 5(1) S1.
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