Following a severe drought in the late 1970s and early 1980s, the invasive shrub Prosopis, a kind of mesquite native to South America, was introduced by international organizations to locations across Kenya's drylands, including the Turkana region in the far north. Prosopis, known as etirae in Turkana, was envisaged as a solution to a range of problems, including deforestation, fuelwood shortages and general environmental deterioration. While exacerbated by drought, these problems were perceived to reflect a much more fundamental crisis, with prevalent views at the time envisaging pastoralism as unsustainable, destructive and in need of overhaul--a narrative dating to colonial times that has since been discredited. Since its introduction, etirae has spread relentlessly, invading riparian land, encroaching on cultivation plots and growing to new heights and thicknesses. Investigating its entanglements with Turkana livelihoods and economic relationships is also a process of understanding how it has braided its way through contested processes of social change, and how it has come to be intertwined with conceptions of cascading crisis quite distinct from the narratives that led to its initial introduction. Implications emerge regarding both the complicated biological residues of past development interventions and the totalizing crisis-oriented narratives that shape drylands development in the current era of climate change. Apres une periode de grave secheresse a la fin des annees 1970 et au debut des annees 1980, des organisations internationales ont introduit le Prosopis, un arbuste envahissant de type mesquite, natif d'Amerique du Sud, dans des regions arides du Kenya comme le Turkana, dans l'extreme nord du pays. Le Prosopis, connu sous le nom d'etirae au Turkana, se voulait comme une solution a de nombreux problemes comme la deforestation, le manque de bois de feu et la degradation generale de l'environnement. Bien qu'exacerbes par la secheresse, ces problemes etaient percus comme le reflet d'une crise bien plus fondamentale, les opinions repandues a l'epoque jugeant le pastoralisme non viable, destructeur et a reformer, un discours datant de la periode coloniale et desormais discredite. Depuis son introduction, l'etirae n'a cesse de se propager, envahissant les terres riveraines, empietant sur les terrains cultives et gagnant en hauteur et en epaisseur. L'etude de ses imbrications avec les moyens de subsistance et les relations economiques dans le Turkana permet egalement de comprendre comment il s'est tresse dans des processus contestes de changement social, et comment il en est venu a s'entremeler avec des conceptions de crise en cascade nettement distinctes des discours qui ont mene a son introduction initiale. Des implications emergent concernant les residus biologiques compliques d'anciennes interventions de developpement et les discours totalisants orientes sur la crise qui faconnent le developpement des regions arides a l'ere du changement climatique. Apos uma grave seca no final da decada de 1970 e inicio da decada de 1980, o arbusto invasor Prosopis, uma especie de mesquite nativa da America do Sul, foi introduzido por organizacoes internacionais em locais das terras secas do Quenia, incluindo a regiao de Turkana, no extremo norte. A Prosopis, conhecida como etirae em Turkana, foi encarada como uma solucao para uma serie de problemas, incluindo a desflorestacao, a escassez de lenha e a deterioracao geral do ambiente. Embora exacerbados pela seca, estes problemas eram vistos como reflexo de uma crise muito mais fundamental, com as opinioes prevalecentes na altura a considerarem a pastoricia como insustentavel, destrutiva e a necessitar de uma revisao--uma narrativa que remonta aos tempos coloniais e que, desde entao, tem sido desacreditada. Desde a sua introducao, a etirae espalhou-se implacavelmente, invadindo terras ribeirinhas, invadindo parcelas de cultivo e crescendo a novas alturas e espessuras. Investigar os seus envolvimentos com os meios de subsistencia e as relacoes economicas da Turkana e tambem um processo de compreensao da forma como a etirae se entrelacou com processos contestados de mudanca social e como se entrelacou com concepcoes de crise em cascata bastante distintas das narrativas que levaram a sua introducao inicial. Surgem implicacoes relativas tanto aos complicados residuos biologicos de intervencoes de desenvolvimento passadas como as narrativas totalizantes orientadas para a crise que moldam o desenvolvimento das terras secas na atual era das alteracoes climaticas., Introduction: tangled crises In the late 1970s and early 1980s, drylands across Africa, from the Sahel to the Horn, experienced an acute environmental crisis. Severe and protracted drought provoked large-scale [...]