尼泊尔用于缓解人与野生动物冲突之电篱笆经济效用分析

人与野生动物冲突是全世界自然保护工作所面临的最大挑战之一。为降低这些冲突的影响,各国采取了各种保护策略,但这些策略常常得不到足够的监测,其效力也得不到充分的评估。近年来,作为降低人与野生动物冲突的一项措施,尼泊尔各保护区周围建起了电篱笆。到目前为止,未见有其他针对保护工作中采用电篱笆的成本效率及其功效开展分析的研究。本研究的目的是检验尼泊尔近年来设立于旺国家公园东区的电篱笆的成本效率。印度犀牛（Rhinoceros unicornis）、野猪（Sus scrofa）、亚洲象（Elephas maximus）、老虎（Panthera tigris）是该国家公园周边缓冲区涉及人与野生动物冲突的主要物种,这里建有电篱笆。电篱笆使庄稼受损减少78%,家畜损失减少30%-60%。研究区的人类死亡数未表现出显著下降,而是继续维持较低数值。我们的分析表明,至2009/2010财政年度,电篱笆成本的总净现值,卡根社区（KMUC）为1 517 959尼泊尔卢比（21 685美元）,姆瑞加社区（MKUC）为3 530 075卢比（50 429美元）;而净现收益,卡根社区为16 301 105卢比（232 872美元）,姆瑞加社区为38 304 602卢比（547 208美元）。至2009/2010基准财政年度,电篱笆的成本-效益比率,卡根社区为10.73,姆瑞加社区为10.85。这些结果表明,在大型哺乳动物出没的保护区周围,电篱笆计划在降低人与野生动物冲突方面,既有经济效益,又有很好的社会效益。     

Episodic gravitational collapse and migration of the mountain chain during orogenic roll‐on in the Himalayas

An ～W–E belt of maximum bulk horizontal shortening (the orogen core) moved North relative to the overlying crust to form the Himalayan Syntaxes due to roll‐on of this portion of the Indian plate. This displacement occurred below a lengthy succession of gently dipping decollements that formed episodically at a depth of ～30 km along the orogen core due to numerous periods of gravitational collapse and spreading of the overlying ductile crust. Successively developed basal decollements were deformed when continued bulk horizontal shortening of the orogen core below reasserted dominance over the effects of gravitational collapse above causing refolding about steeply dipping axial planes. This resulted in northwards migration of the orogen core above depths of ～30 km causing rocks metamorphosing at depths of ～22 km on the north side of the orogen core to be moved to its south side with no change in depth as roll‐on progressed. Garnet porphyroblasts record this lengthy history of lateral migration across the orogen within their inclusion trails. The ～6.4 kbar average pressures accompanying it were obtained from the Mn, Fe and Ca contents of successive garnet cores. Garnet grew at depths of ～22 km until movement towards the surface initiated on successively developed decollements that accommodated the volume constraints of gravitational collapse and spreading on both sides of the orogen. The speed of extrusional displacement increased the further the rocks migrated from the orogen core developing mylonitic schists around the porphyroblasts. This truncated inclusion trails against all matrix foliations as the porphyroblasts were carried towards the surface. Indeed, these rocks were multiply deformed during at least four distinct periods of deformation after mylonitization began and prior to exposure above the Main Central Thrust (MCT). Three or more sub‐vertical and sub‐horizontal foliations were formed during each of the five changes in FIA trend (foliation inflection/intersection axes in porphyroblasts) preserved in these rocks. The inclusion trail asymmetries and P‐T of garnet core growth accompanying each FIA reveal that the first four changes in FIA trend, which define periods of tectonism about one direction of horizontal bulk shortening (relative plate motion), occurred on the north side of the orogen core. The fifth occurred on the south side of the orogen core and the switch in shear sense on gently dipping foliation planes that resulted from this shift to the south eventually led to the development of the MCT. When magnetic anomaly 22 that formed in the Southern Indian Ocean Ridge is taken into account, these five changes in FIA trend correlate markedly with changes in the motion of India relative to a constant Eurasia from 50 to c. 25 Ma. They reveal that Eurasia moved NNW during FIAs 1, 3 and 4 and SSE during FIA 5 when the shear sense on gently dipping foliations switched to top to the S. They suggest collision of India with Eurasia took place at 50 Ma, immediately prior to the development of FIA 1.