南方红壤侵蚀区不同恢复年限马尾松人工林土壤和叶片氮磷养分含量及生态化学计量特征

植被恢复是我国水土侵蚀地区的重要治理措施.南方红壤丘陵区是我国第二大水土流失区,但针对该地区植被恢复过程中土壤氮(N)和磷(P)养分动态研究依然不足,尤其关于1 m深土壤N和P养分特征尚未见报道.以南方红壤严重水土侵蚀区不同植被恢复年限林地(裸地、10年、20年和30年生马尾松人工林和天然次生林)为研究对象,比较植物叶片和1 m深度土壤N和P含量及生态化学计量比特征.结果显示:随着马尾松人工林恢复年限增加,0-10 cm土壤N含量显著提高,但深层( 10 cm)土壤N含量并无显著差异,与地带性天然次生林相比,马尾松人工林各土层土壤N含量依然显著偏低;随着恢复年限增加,马尾松人工林各层土壤全P含量未显著提高,且裸地、10年、20年生马尾松人工林和天然次生林各土层土壤全P含量差异不显著;随着恢复年限增加,植物叶片N和P含量呈增加趋势,与未经治理的裸地相比,30年生马尾松人工林叶片N和P含量分别增加42.26%和27.17%,且植物叶片N和P含量与各层土壤N和P养分存在显著正相关关系.本研究表明南方红壤严重侵蚀区土壤N和P养分对植被恢复的响应存在差异;与土壤P养分相比,土壤N养分能够不断增加.施加磷肥措施促进了红壤水土侵蚀区植被恢复,并促进单一马尾松人工林转变为地带性天然次生林植被.(图3表1参46)     

亚热带红壤侵蚀退化区不同恢复水平生境内先锋树种竞争特征

以亚热带红壤侵蚀退化区先锋树种马尾松(Pinus massionana Lamb.)和木荷(Schima superba Gardn. et Champ)为研究对象,设置4个不同恢复水平样地,构建Voronoi图确定林木生长空间和邻近竞争木,采用V_Hegyi竞争指数定量分析亚热带红壤丘陵生态恢复早期不同生境恢复阶段先锋树种竞争特征.结果显示:对象木个体竞争强度与其胸径服从幂函数关系(CI=AD~B);随着个体胸径的增大,个体受到的竞争压力逐渐减弱.林木竞争结构和竞争强度在不同样地间具有显著差异(P 0.005),其全林分个体平均竞争强度依次为中等恢复水平样地(3.839 63)强度侵蚀水平样地(2.315 83)阔叶树进入样地(2.019 12)较高恢复水平样地(1.084 75).本研究表明从马尾松占优势的针叶林阶段向针阔混交阶段的生态过程中,林木竞争指数呈现先升后降的趋势,竞争在驱动群落发生演替的同时又受到群落结构变化和个体生长状况的影响而不断调整;因此针对不同生境恢复水平应采取相应措施,以减小竞争对生境恢复带来的不利影响.(图3表4参39)     

漓江流域红壤区生态恢复过程中植被结构动态和生物量变化

利用时空替代原理，选取漓江流域红壤区退化生态系统恢复过程中具有代表性的草丛、灌丛、针叶林、针阔混交林、常绿阔叶林5个阶段作为演替序列，研究自然恢复过程中各演替阶段的植被结构动态和生物量变化。结果表明：随着草丛→灌丛→针叶林→针阔混交林→次生常绿阔叶林正向演替的进行，在未形成成熟而稳定的顶极群落之前，物种丰富度、物种多样性指数、植被生物量及生产力都呈增大趋势。退化群落通过自然恢复总是向着结构更复杂、更完善的方向发展。根据恢复过程中植被的动态变化规律，提出了一些人工促进植被恢复的建议．     

亚热带次生常绿阔叶林优势种间的竞争效应与竞争反应

运用邻体干扰模型及其野外工作方法,初步研究了缙云山亚热带次生常绿阔叶林优势种马尾松(Pinus massoniana)、大头茶(Gordonia acumenata)和白毛新木姜子(Neolitea aurata var. glauca)3个种群间的竞争效应与竞争反应.结果表明(1)种内竞争效应排序为马尾松＞大头茶＞白毛新木姜子;(2)种间竞争效应排序为白毛新木姜子＞马尾松＞大头茶;(3) 种间竞争反应排序为大头茶＞马尾松＞白毛新木姜子;(4)白毛新木姜子与大头茶之间的竞争强度最大,达到1.05;大头茶与马尾松之间的竞争强度最小,仅为0.32. 表3 参8     

南京南郊马尾松种群动态及种内竞争模型的应用

通过对南京南郊马尾松(Pinus massoniana)种群年龄结构的统计,绘制该种群的静态生命表。结果表明,该马尾松种群年龄结构属衰退型;存活曲线为凸形曲线,属Deevey-A型;死亡率和消失率变化规律一致,均在第11龄级(47~49 a)时取得极大值,分别达0.625和0.981。对群落Hegyi竞争指数的计算表明,种内竞争是马尾松种群衰退的主要原因:种内竞争指数占总竞争指数的85.8%,种内平均单木竞争指数为1.71,而种间竞争指数仅占总竞争指数的14.2%。非线性回归结果表明,用林振山种内竞争模型拟合南京南郊马尾松种群数量的衰退规律可以达到较高优度,判定系数为0.759,此地马尾松种群固有出生率为0.105,环境对马尾松的最大容量为31株·(400 m2)-1。模型稳定性分析表明,马尾松种群虽然处于衰退阶段,但种群不会退出该地区,并将在未来很长时间保持群落优势种的地位,种群密度最终将衰退至9.396株·(400 m2)-1的稳定状态。     

三种木本植物对酸雨的敏感性和抗性

酸雨污染对生态系统和人类生存环境造成严重影响,研究植物抗性及其对环境的适应能力是大气污染胁迫退化生态系统恢复中植物种类选择的基础和前提。作者选择陶瓷工业污染区南海西樵山和相对清洁区肇庆鼎湖山自然生长的木本植物鸭脚木(Schefflera octophylla)、荷木(Schima superba)当年生叶和一年生叶以及马尾松(Pinus massoniana)一年生针叶进行生理指标的测定和分析。结果表明:在酸雨污染环境下,3 种植物叶片的细胞膜透性受到损害,光合色素降解,PSII 最大光化学效率下降;对酸雨污染的敏感性次序为:马尾松>鸭脚木≥荷木,马尾松为酸雨敏感种。初步讨论了树木对酸雨污染的部分抗性生理机制,为酸雨污染地区退化生态系统恢复之植被选择提供理论依据。     

不同恢复年限退化土壤有机氮组分变化特征

为明确退化土壤在不同恢复年限下土壤有机氮组分变化规律,以福建长汀县退化红壤为研究对象,利用时空替代法,选取5个典型的不同植被恢复阶段样地,分别为裸地,恢复7、17、23、35a的马尾松(Pinusmassoniana)人工林,采用Bremner酸水解法研究土壤有机氮各组分的变化特征。结果表明,与裸地相比,恢复年限为7、17、23、35a的土壤全氮含量分别增加了2.57、3.71、4.00、5.57倍,且主要以酸解性氮形态存在。酸解性氮和非酸解性氮含量均随全氮含量的增加而显著提高(P<0.01),但植被恢复提高了非酸解氮比例,降低了酸解性氮比例。土壤氨态氮、氨基酸态氮和酸解未知态氮含量随着恢复年限的延长而提高;酸解性总氮含量与氨态氮、氨基酸态氮和酸解未知态氮含量呈显著正相关(P<0.01)。线性回归斜率表明,不同恢复年限土壤增加的酸解性总氮中12.4%为氨态氮、47.3%为氨基酸态氮、35.2%为酸解未知态氮、5.1%为氨基糖态氮。植被恢复降低了氨态氮组分占酸解性总氮的比例,提高了氨基酸态氮组分占酸解性总氮的比例。有机氮组分特征变化影响土壤氮素供应与贮存能力。该研究结果可为退化土壤恢复过程养分管理提供参考。     

海州露天煤矿排土场植被恢复的土壤水文效应评价

为揭示排土场复垦区植被恢复的土壤水文效应,选取12个环境因子作为排土场植被恢复过程中土壤水文效应评价指标,采用层次分析法确定各评价指标权重,建立排土场土壤水文效应评价指标体系和评价模型,并对6种复垦植被类型下(刺槐Robinia pseudoacacia林地、榆树林地、混交林地、灌木林地、农地和荒草地)土壤水文效应进行评价。结果表明:(1)土壤因子、水分因子和植被因子的权重值分别为0.513 8、0.193 0和0.293 2,各个评价指标的综合权重在0.031 8~0.146 2之间;(2)排土场不同植被恢复模式的土壤水文效应综合指数大小顺序为刺槐林地(0.553 85)混交林地(0.534 9)榆树林地(0.521 3)灌木林地(0.429 2)荒草地(0.375 3),较农地(0.361)分别提高53.41%、48.17%、44.4%、18.89%和3.96%;(3)植被恢复可以有效地改善排土场的土壤水文效应,且以乔木林恢复效果更佳。该研究可为排土场不同植被恢复过程中土壤水文效应的评价提供较为科学的评价指标体系,同时为排土场土地复垦和生态恢复与重建提供理论依据和新的分析角度。     

湘北红壤坡地生态恢复过程中的植被演变

采用森林资源清查调查相关植被指标(Simpson指数,物种均匀度指数和多样性指数)的方法,对湘北红壤坡地恢复区和退化区近20年来生态恢复过程中植被演变,生物生产力及碳平衡的变化情况进行了初步调查分析。结果表明,(1)恢复区植被在20年间经历了缓慢恢复、快速恢复和物种逐渐减少3个阶段,物种由32种增加至73种;退化区物种经历了先减少、后增加、再急剧减少3个阶段,物种由43种减少至27种。(2)恢复区草本的Simpson指数持续减少,灌木草本无明显规律,草本和灌木的物种均匀度呈降低态势,乔木多样性指数变化规律不明显;退化区草本各项多样性指标无明显变化趋势,灌木各项多样性指数均在稳步提高。(3)恢复区生物量和碳量稳步提高,2003─2012年间植被含碳量增加到原来的1.48倍;退化区生物量和含碳量总体下降,2003─2013年间植被含碳量从387 g·m-2降低到356.9 g·m-2。     

科尔沁沙地恢复过程中地上定植群落与土壤种子库特征及其关系研究

选择科尔沁沙地固定沙地、半流动沙地和流动沙地样地,研究沙地恢复过程中土壤种子库密度、组成及其与地上植被的关系。结果表明,(1)退化沙地恢复过程中,流动沙地、半流动沙地、固定沙地的土壤种子库平均密度(以单位面积有效种子数量表示,ind·m~(-2))分别为814、3 125和16 294 ind·m~(-2)。土壤种子库物种组成以一年生草本为主,多年生植物和灌木类所占的比例小。(2)地上定植群落与土壤种子库的变化趋势一致,地上定植群落的平均密度分别为68、242和673 plant·m~(-2)。地上定植群落物种组成也以一年生植物为主,但所占比例较土壤种子库有所下降。(3)不管是土壤种子库还是地上定植群落,Shannon-Wiener指数、Simpson指数、均匀度指数和丰富度指数大小顺序均为:固定沙地半固定沙地流动沙地,土壤种子库物种多样性指数均大于地上植被。(4)地上植被与土壤种子库组成上的相似性系数在0.333~0.739之间,相似性系数较高。地上定植群落与土壤种子库密度存在显著的正相关关系。流动沙地、半流动沙地、固定沙地地上植被密度分别有36%、52%、60%的变异可归结为土壤种子库密度的变异。科尔沁沙地土壤种子库是地上植被自然恢复的重要物质基础,土壤种子库中的大量种子,在植被自然恢复中将发挥积极的作用。     

Achieving Open Access to Conservation Science

Conservation science is a crisis discipline in which the results of scientific enquiry must be made available quickly to those implementing management. We assessed the extent to which scientific research published since the year 2000 in 20 conservation science journals is publicly available. Of the 19,207 papers published, 1,667 (8.68%) are freely downloadable from an official repository. Moreover, only 938 papers (4.88%) meet the standard definition of open access in which material can be freely reused providing attribution to the authors is given. This compares poorly with a comparable set of 20 evolutionary biology journals, where 31.93% of papers are freely downloadable and 7.49% are open access. Seventeen of the 20 conservation journals offer an open access option, but fewer than 5% of the papers are available through open access. The cost of accessing the full body of conservation science runs into tens of thousands of dollars per year for institutional subscribers, and many conservation practitioners cannot access pay‐per‐view science through their workplace. However, important initiatives such as Research4Life are making science available to organizations in developing countries. We urge authors of conservation science to pay for open access on a per‐article basis or to choose publication in open access journals, taking care to ensure the license allows reuse for any purpose providing attribution is given. Currently, it would cost $51 million to make all conservation science published since 2000 freely available by paying the open access fees currently levied to authors. Publishers of conservation journals might consider more cost effective models for open access and conservation‐oriented organizations running journals could consider a broader range of options for open access to nonmembers such as sponsorship of open access via membership fees. Obtención de Acceso Abierto a la Ciencia de la Conservación     

Rapid,recurring, structured survey versus bioblitz for generating biodiversity data and analysis with a multispecies abundance model

A bioblitz inexpensively and quickly generates biodiversity data, but bioblitzes are often conducted with haphazard, unreplicated sampling. Results tend to be taxonomically, geographically, or temporally biased, lack metadata, and consist of lists of observed taxa that do not enable further analyses or correction for imperfect detection. A rapid, recurring, structured survey (RRSS) uses a structured sampling design and temporal and spatial replication to survey randomly selected sites on a conservation property. We participated in a loosely structured bioblitz and a subsequent RRSS at Big Canoe Creek Nature Preserve in Springville (St. Clair County), Alabama (USA) to compare observed richness derived from the 2 survey approaches. The RRSS data structure enabled us to fit models that accounted for imperfect detection to estimate abundances, occupancy probabilities, and habitat associations. The loosely structured bioblitz data could not be used in such models. We present a new integrated multispecies abundance model that we applied to avian RRSS data. Our model extension enables estimation for the community, employs data augmentation to estimate the number of undetected species, and incorporates covariates. The RRSS generated a more comprehensive and less biased list of observed taxonomic richness than the loosely structured bioblitz (e.g., 73 vs. 45 bird species and 104 vs. 63 insect families from the RRSS vs. loosely structured bioblitz, respectively). Models fit to the RRSS data identified seasonal patterns in avian community composition and allowed for estimation of habitat–occupancy relationships for insect taxa. The RRSS protocol has potential for broad transferability as a standardized, quick, and inexpensive way to inventory biodiversity and estimate ecological parameters while providing an outreach opportunity.     

Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters

Land-use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland and creek), offsetting measure (e.g., enhancement, restoration, and creation), and an assessment of the projects’ compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.     

A palaeo-hydrogeological model for arsenic contamination in southern and south-east Asia

An argument is presented in which areas of natural arsenic contamination of modern groundwaters throughout Asia have a common origin. Arsenic originally accumulated in oceanic ferro-manganoan sediments of the eastern Palaeo-Tethys. This was further concentrated through oceanic crustal extinction in what later became the south-east Chinese accreted mineralised terrain. Proto-Himalayan uplift of this area created the palaeo-drainage systems of the Ganges – Brahmaputra, Irrawaddy, Mekong, and Red Rivers, with consequent headwater erosion of arsenic-rich sediments. Their downstream deposition as immature and easily redistributed Neogene sandstones, silts, and iron-rich clays has created secondary and tertiary reservoirs of adsorbed and authigenic arsenic, from which the current arsenic-rich groundwaters have evolved. Considering river basins within the above palaeo-hydrogeological framework provides a basis for assessing the risk of arsenic in groundwater basins of south and south-eastern Asia.     

Sequestration of cucurbitacin analogs by New and Old World chrysomelid leaf beetles in the tribe Luperini

Summary Two South American polyphagous leaf beetles,Diabrotica speciosa andCerotoma arcuata, selectively accumulated the bitter tasting compound 23,24-dihydrocucurbitacin D in their body after ingesting root tissues of cucurbit plants. Similarly, three Asian Cucurbitaceae-feeding specialists in the genusAulacophora were found to sequester the same compound. Cucurbitacin analogs were shown to deter feeding by a bird predator, indicating an allomonal role for these compounds in cucurbitacin-associated chrysomelid leaf beetles both of New and Old Worlds. The strong affinity to cucurbitacins, selective sequestration of the analogs and consequent protection from predators suggested an ecological adaptation mechanism developed in common among these two geographically isolated subtribes in the Luperini.     

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

Abstract: In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9‐ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3‐year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more‐lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already‐declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.     

Cost‐effective conservation of an endangered frog under uncertainty

How should managers choose among conservation options when resources are scarce and there is uncertainty regarding the effectiveness of actions? Well‐developed tools exist for prioritizing areas for one‐time and binary actions (e.g., protect vs. not protect), but methods for prioritizing incremental or ongoing actions (such as habitat creation and maintenance) remain uncommon. We devised an approach that combines metapopulation viability and cost‐effectiveness analyses to select among alternative conservation actions while accounting for uncertainty. In our study, cost‐effectiveness is the ratio between the benefit of an action and its economic cost, where benefit is the change in metapopulation viability. We applied the approach to the case of the endangered growling grass frog (Litoria raniformis), which is threatened by urban development. We extended a Bayesian model to predict metapopulation viability under 9 urbanization and management scenarios and incorporated the full probability distribution of possible outcomes for each scenario into the cost‐effectiveness analysis. This allowed us to discern between cost‐effective alternatives that were robust to uncertainty and those with a relatively high risk of failure. We found a relatively high risk of extinction following urbanization if the only action was reservation of core habitat; habitat creation actions performed better than enhancement actions; and cost‐effectiveness ranking changed depending on the consideration of uncertainty. Our results suggest that creation and maintenance of wetlands dedicated to L. raniformis is the only cost‐effective action likely to result in a sufficiently low risk of extinction. To our knowledge we are the first study to use Bayesian metapopulation viability analysis to explicitly incorporate parametric and demographic uncertainty into a cost‐effective evaluation of conservation actions. The approach offers guidance to decision makers aiming to achieve cost‐effective conservation under uncertainty.     

Parasitic wasps orient to green leaf volatiles

Summary Undamaged plants emit low levels of green leaf volatiles (GLVs), while caterpillar-damaged and artificially damaged plants emit relatively higher levels of certain GLVs. Female braconid parasitoids,Microplitis croceipes, oriented to both damaged plants and to individual GLVs in no-choice tests in a wind tunnel, but seldom oriented to undamaged plants. Female ichneumonid parasitoids,Netelia heroica, also oriented to individual GLVs in a wind tunnel. Males of both wasp species failed to orient to the GLVs. These data show that leaf-feeding caterpillars can cause the release of GLVs, and that parasitic wasps can respond to these odors by flying upwind (chemoanemotactic response), which brings the wasps to their caterpillar hosts. This supports the hypothesis that plants communicate with members of the third trophic level,i.e., plants under herbivore attack emit chemical signals that guide natural enemies of herbivores to sites of plant damage. In this interaction, the GLVs serve as tritrophic plant-to-parasitoid synomones. That parasitoids from two different wasp families oriented to GLVs suggests that the response may be widespread among the Hymenoptera.Mention of a commercial or proprietary product does not constitute an endorsement by the U.S. Department of Agriculture     

What Every Conservation Biologist Should Know about Economic Theory

Abstract: The last century has seen the ascendance of a core economic model, which we will refer to as Walrasian economics. This model is driven by the psychological assumptions that humans act only in a self‐referential and narrowly rational way and that production can be described as a self‐contained circular flow between firms and households. These assumptions have critical implications for the way economics is used to inform conservation biology. Yet the Walrasian model is inconsistent with a large body of empirical evidence about actual human behavior, and it violates a number of basic physical laws. Research in behavioral science and neuroscience shows that humans are uniquely social animals and not self‐centered rational economic beings. Economic production is subject to physical laws including the laws of thermodynamics and mass balance. In addition, some contemporary economic theory, spurred by exciting new research in human behavior and a wealth of data about the negative global impact of the human economy on natural systems, is moving toward a world view that places consumption and production squarely in its behavioral and biophysical context. We argue that abandoning the straightjacket of the Walrasian core is essential to further progress in understanding the complex, coupled interactions between the human economy and the natural world. We call for a new framework for economic theory and policy that is consistent with observed human behavior, recognizes the complex and frequently irreversible interaction between human and natural systems, and directly confronts the cumulative negative effects of the human economy on the Earth's life support systems. Biophysical economics and ecological economics are two emerging economic frameworks in this movement.