Prosopis pallida

Prosopis pallida
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Fabales
Family:	Fabaceae
Subfamily:	Caesalpinioideae
Clade:	Mimosoid clade
Genus:	Prosopis
Species:	P. pallida
Binomial name
	Prosopis pallida; (Humb.&Bonpl.exWilld.)Kunth
Synonyms
	Acacia pallidaHumb.&Bonpl.exWilld.; Prosopis limensisBenth.;

Prosopis pallidais a species ofmesquitetree. It has the common nameskiawe(/kiːˈɑːveɪ/)^[2](in Hawaii),huarango(in its native South America) andAmerican carob,as well as "bayahonda" (a generic term forProsopis), "algarrobo pálido" (in some parts of Ecuador and Peru), and "algarrobo blanco" (usually used forProsopis alba). It is a thornylegume,native toColombia,EcuadorandPeru,^[2]particularly drier areas near the coast. While threatened in its native habitat, it is considered aninvasive species^[2]in many other places.

Description

The kiawe is a spreading bush or moderately sized tree, bearing spines, spikes of greenish-yellowflowers,and longpodsfilled with small brownseeds.It is a successful invasive species due to its ability to reproduce in two ways: production of large numbers of easily dispersed seeds, andsuckeringto create thick monotypic stands that shade out nearby competing plants. It survives well in dry environments due to a longtaprootwhich can reach deep watertables. It is so efficient at extracting moisture from soil that it can kill nearby plants by depriving them of water, as well as by shading them out. It can be found in areas where other plants do not grow, such as sandy, dry, degraded slopes,saltysoils,disturbed areas,and rocky cliffs.

Human uses

The tree grows quickly and can live for over a millennium. It makes a good shade tree, if one does not mind the nasty thorns of the fallen branches. Its hard wood is a source of long-burning firewood^[2]andcharcoal.^[3]Kiawe pods can be used aslivestockfodder,^[2]ground into flour, turned intomolassesor used to makebeer.^[3]The light yellow flowers attractbees,which produce from them a sought-after whitehoney.^[4]

Hazards to humans

Fallen Kiawe branches usually contain sharp spines that can puncture both feet and tires.

Status as an invasive species in Hawaii

At times the tree was used to replace forest and preventerosion,and once it was established it generally dominates the habitat. It was introduced toPuerto Ricoand Hawaii as well asNew South Walesand Queensland in Australia and is nownaturalizedin those places. The first kiawe was planted in Hawaii in 1828;^[2]today it is a ubiquitous shade tree and invasive weed on theHawaiian Islands,but providesfirewoodfor heating and cooking.^[5]

Collapse of the Nazca culture

The clearing of kiawe (huarango) has been suggested as a major reason for the collapse of theNazca culturein southern Peru at the beginning of the 6th century AD after anEl Niñoevent led to flooding,erosionanddesertification.^[6]

Importance in the desert ecosystem

Ecologists consider the huarango important to the ecosystem of the desert area west of theAndesin southern Peru, because of its ability to bind moisture and counter erosion. Despite prohibitions by regional authorities, poor villagers continue to harvest the trees to make charcoal. Efforts are under way to reforest the area with huarangos.^[3]^[7]^[8]

Genetic variability

In the southwest of Ecuador,Prosopis pallidaandProsopis julifloraboth display substantial genetic variability due to the (intraspecific) cross-pollination of theirself-incompatibleflowers which are typical of the genusProsopis.As a result, trees of these species display a range of physical traits that lead to trees of one species resembling descriptions of the other, and the two species are often confused. To compound the difficulty in discerning the species of a given tree, these two species hybridise readily where their ranges overlap.^[9]In thesemi-arid Zapotillo Cantonof Ecuador, both thorn-bearing and thornless strains ofProsopis pallidaexist with thorn-bearing trees being more common. It is the preferred tree of the local people for making charcoal and is sometimes also cut for firewood or fence posts.