of social science and medicine, 63, 3113 - 3123. tilman, d ( 1999 ), “ the ecological consequences of changes in biodiversity : a search for general principles ”, ecological society of america, vol. 80, no. 5 : 1455 - 1474. voute, a. d ( 1946 ), “ regulation of the density of the insect populations in virgin forests and cultivated woods ”, archives neerlandaises de zoologie, 7, 435 - 470. watts, d ( 2002 ), “ a simple model of global cascades on random networks ”, proceedings of the national academy of sciences 9 : 5766 - 5771. watts, d. j and strogatz, s. h ( 1998 ), “ collective dynamics of'small - world'networks ”, nature 393 ( 6684 ) : 409 – 10. wheelis, m ( 2002 ), “ biological warfare at the 1346 siege of caffa ”, emerging infectious diseases, vol. 8, no. 9. worm, b, barbier, e. b, beaumont, n, emmett duffy, folke c, halpern, b. s, jackson, j. b. c, lotze, h. k, micheli, f, palumbi, s. r, sala, e, selkoe, k. a and stachowicz, j. j ( 2006 ), “ impacts of biodiversity loss on ocean ecosystem services ”, science, vol. 314 : 787790. tables : table 1 : summary statistics on the global financial network skewness 7. 4 8. 0 3. 1 kurtosis 71. 3 80. 6 14. 3 average path length 1. 55 1. 44 1. 37 table 2 : climbing the complexity tree typical contract details ( a ) pages in cdo ^ 2 prospectus pages in abs cdo prospectus pages in rmbs prospectus number of abs cdo tranches in cdo ^ 2 number of rmbs in a typical cdo number of mortgages in typical rmbs 5, 000 metrics of complexity ( a ) [ 1 ] + [ 3 ] * [ 5 ] * [ 2 ] * [ 4 ] pages to read for a cdo ^ 2 investor 1, 125, 000, 300 [ 2 ] + [ 3 ] * pages to read for an abs cdo investor 30, 300 [ 4 ] * [ 5 ]

financial instruments served to amplify further network fragility. diversity and stability a final dimension to network robustness concerns the effects of diversity. the oceans provide a rich and lengthy test - bed of the links between diversity and robustness. over the past millennium, studies of coastal eco - systems reveal some dramatic patterns. 18 for around 800 years, between the years 1000 - 1800ad, fish stocks and species numbers were seemingly stable and robust. since then, almost 40 % of fish species across the world ’ s major the results here are based on worm et al ( 2006 ). coastal eco - systems have “ collapsed ”, defined here as a fall in population of greater than 90 %. that is systemic by any metric. there appear to be many environmental reasons for this collapse, some natural, others manmade. but the distribution of this collapse across eco - systems is revealing. for species - rich – that is, diverse – eco - systems the rate of collapse has been as low as 10 % ; for species - poor eco - systems, as high as 60 %. diverse coastal eco - systems have proved to be markedly more robust, measured over century spans. results for large marine eco - systems suggest a similar picture. over the period 1950 - 2003, the incidence of collapsed fisheries declines exponentially with species - diversity. 19 diversity also appears to increase the resilience of fisheries – that is, their capacity to recover – in the event of collapse. these results reappear throughout marine eco - systems, “ in coral reefs in jamaica and on rocky shores in panama ”. 20 and they do not appear to be unique to marine eco - systems. for example, similar effects of diversity have been found in studies of the resilience of crops to pathogen outbreaks ; in the robustness of savannas and grassland to drought ; and in morbidity and mortality rates among humans facing disease and infection. 21 diversity of the gene pool, it seems, improves durability. the financial system has mirrored the fortunes of the fisheries, for many of the same reasons. since the start of 2007, 23 of the largest european and us banks have seen their market capitalisation fall by 90 % or more – the fisheries equivalent of collapse. but what took marine eco - systems two hundred years to achieve has been delivered by financial engineers in two. in explaining the collapse in fish and finance, lack of diversity seems to be a common denominator. within the financial sector, diversity appears to