Invasive Plants of Saudi Arabia
Invasive alien species have distressing impacts on native biota, causing decline or even extinctions of native populations. All major invasions are due to deliberate or unintentional actions of humans, birds, animals and, to a certain extent, due to traffic across the borders. Though majority of introductions have only minor impacts to the ecosystem, some of them led to numerous problems. The vegetation of Saudi Arabia, particularly of the plant diversity hotspots in the southwestern region including some of the Red Sea Islands is inundated by the influx of several alien plants. Fifty two exotic species have been recorded from Saudi Arabia, some of which have entered and naturalized in the Kingdom several decades ago. Among these, 44 are from American continents, 4 from Tropical countries, 2 from Australis and one each from East Asia, South Asia and Iran. All major invasive species in Saudi Arabia are native to American Continents. Among these, the species that potentially damaging the biodiversity or altering the ecosystems in general are: Argemone ochrolecuca, Nicotiana glauca, Opuntia dellenii, O. ficus-indica, Prosopis juliflora and Trianthema portulacastrum.
Prosopis juliflora is the most troublesome invasive species in majority of places in Tihama. Among the major invaders, four species (Argemone ochroleuca, Nicotiana glauca, Opuntia dellenii, O. ficus-indica,) have been seen in areas above 1000 meters while Prosopis juliflora and Trianthema portulacastrum have been observed in areas below 800 m and in areas between 100-1500 m respectively. Opuntia spp. showed a preference for warm and dry climates and are common on the east facing slopes of southwestern highlands; while N. glauca responded well to low temperature and high precipitation rates. P. juliflora, Argemone spp. and Nicotiana glauca illustrated a strong association with high levels of human influence, proximity to urban and disturbed areas.
Vegetation of the northwestern Hijaz Mountain is less affected by invasions. Only P. juliflora and Cuscuta campestris are the major exotic species seen among the communities of lowlands and slopes of the mountains. The influence of exotic species in the central and eastern regions are also less significant. P. juliflora, Cuscuta campestris, Cenchrus echinatus, Euphorbia spp., Verbesina encelioides, Leucaena leucocephala, Prosopis koelziana, etc. are the main invaders spotted among native plant populations. Unlike the southern islands in the Red Sea (Farasan Al-Kabir), islands of Arabian Gulf are devoid of exotic species, except for a few Prosopis juliflora plants close to the farms of one of the inhabited islands, Jana Island, off Jubail coast.
Exotic Invaders.
| Species | Family | Geographical Distribution | Habit | Degree of infestation |
| Alternanthera pungens | Amaranthaceae | Southwestern Mountains | Herb | Low |
| Amaranthus albus | Amaranthaceae | Central, Eastern and | Herb | Low |
| Western regions | ||||
| Amaranthus hybridus | Amaranthaceae | Throughout Saudi Arabia | Herb | Low |
| Amaranthus spinosus | Amaranthaceae | Southwestern mountains | Herb | Low |
| Annona squamosa | Annonaceae | Southwestern mountains | Tree | Low |
| (Jabal Fayfa) | ||||
| Argemone mexicana | Papaveraceae | Southwestern mountains | Herb | Medium |
| Argemone ochroleuca | Papaveraceae | Southwestern mountains | Herb | High |
| Astrocylindropuntia subulata | Cactaceae | Southwestern mountains | Shrub | Low |
| (Presence not confirmed) | ||||
| Atriplex suberecta | Chenopodiaceae | Central and eastern regions | Herb | Medium |
| Bidens aurea | Asteraceae | Southwestern mountains | Herb | Low |
| Cenchrus echinatus | Leguminosae | Central, East, West and | P. grass | Medium |
| West regions | ||||
| Cenchrus setigerus | Poaceae | Southwestern mountains | P. grass | Low |
| Dysphania carinata | Amaranthaceae | Southwestern mountains | Herb | Medium |
| (=Chenopodium carinatum) | ||||
| Chenopodium atrovirens | Amaranthaceae | Central region | Herb | Low |
| Chenopodium desiccatum | Amaranthaceae | Central region | Herb | Low |
| ssp. leptophylloides | ||||
| Cuscuta campestris | Cuscutaceae | Central , eastern and | Herb | Medium |
| northern regions | ||||
| Cylindropuntia imbricata ssp. rosea | Cactaceae | Southwestern region | Shrub | Low |
| Datura ferox | Solanaceae | Southwestern region | Herb | Low |
| Datura innoxia | Solanaceae | Through out Saudi Arabia | Herb | Medium |
| Datura metel | Solanaceae | Southwestern region | Herb | Low |
| Datura stramonium | Solanaceae | Southwestern region | Herb | Medium |
| Dysphania ambrosioides | Amaranthaceae | Central and southwestern | Herb | Low |
| regions | ||||
| Eclipta prostrata | Asteraceae | Central | Shrub | Low |
| Encelia farinosa | Asteraceae | Southwestern region | Shrub | Low |
| Erigeron bonariensis | Asteraceae | Through out Saudi Arabia | Herb | Medium |
| Erigeron canadensis | Asteraceae | Southwestern region | Herb | Low |
| Euphorbia cyathophora | Euphorbiaceae | Eastern Province | P. Herb | Low |
| Euphorbia heterophylla | Euphorbiaceae | Eastern province | P. herb | Low |
| Euphorbia hirta | Euphorbiaceae | Throughout Saudi Arabia | Herb | Medium |
| Euphorbia hypercifolia | Euphorbiaceae | Central and Western regions | Herb | Low |
| Euphorbia maculata | Euphorbiaceae | Central region | Herb | Low |
| Euphorbia prostrata | Euphorbiaceae | Central region | Herb | Low |
| Euphorbia supina | Euphorbiaceae | Central region | Herb | Low |
| Euphorbia tirucalli | Euphorbiaceae | Southwestern region | Low | |
| Shrub/ Tree | ||||
| Flaveria trinervia | Asteraeae | All regions in Saudi Arabia | Herb | Medium |
| Galinsoga parviflora | Asteraeae | Southwestern region | Shrub | Low |
| Heliotropium curassavicum | Boraginaceae | Eastern, central and | Herb | Low |
| southwestern regions | ||||
| Ipomoea carnea ssp. fistulosa | Convolvulaceae | Tihama, SW region | Shrub | High |
| Jatropha curcas | Euphorbiaceae | Southwestern region | Shrub | Low |
| Lantana camara | Verbenaceae | Southwestern mountains | Shrub | Medium |
| Leucaena leucocephala | Leguminosae | Central, eastern and | Tree | Medium |
| southern regions | ||||
| Malvastrum coromandelianum | Malvaceae | Central region | P. Herb | Low |
| Nicotiana glauca | Solanaceae | Asir and Jazan Mountains | Shrub | High |
| Operculina turpethum | Convolvulaceae | Southwestern region | P. Herb | Low |
| Opuntia stricta | Cactaceae | Southwestern region | Shrub | High |
| Opuntia ficus-indica | Cactaceae | Southwestern region | Shrub | High |
| Parthenium hysterophorus | Asteraceae | Southwestern region | Herb | Medium |
| Paspalum dilatatum | Poaceae | Southwestern region | Annual | Low |
| Physalis peruviana | Solanaceae | Tihama, SW region | Herb | Low |
| Physalis stepelioides | Solanaceae | Tihama, SW region | Herb | Low |
| Potamogeton perfoliatus | Potamogetonaceae | Central region | P. Herb | Low |
| Neltuma juliflora | Leguminosae | All regions in Saudi Arabia | Tree | High |
| Prosopis koelziana | Leguminosae | Central region | Tree | Medium |
| Senna occidentalis | Leguminosae | Central and western regions | Shrub | Medium |
| Senna obtusifolia | Leguminosae | Southwestern region | Shrub | Low |
| Sesuvium portulacastrum | Aizoaceae | Eastern and central region | P. Herb | Low |
| Sesuvium verrucosum | Aizoaceae | Central and Western region | Herb | Low |
| Tagetes minuta | Asteraceae | Southwestern region | P. Herb | Medium |
| Trianthema portulacastrum | Aizoaceae | Southwestern region | Herb | Medium |
| Tridax procumbens | Asteraceae | Southwestern region | Herb | Medium |
| Verbesina encelioides | Asteraceae | Southwestern region | Herb | Medium |
| Xanthium spinosum | Asteraceae | Southwestern region | P. Herb | Low |
Native Invaders
| Arundo donax | Poaceae | Throughout Saudi Arabia | Perennial grass | Low |
| Calotropis procera | Apocynaceae | Throughout Saudi Arabia (except high altitude regions) | Shrub | High |
| Desmostachya bipinnata | Poaceae | Throughout Saudi Arabia | Perennial grass | Low |
| Imperata cylindrica | Poaceae | Eastern, northern and southwestern regions | Perennial grass | Medium |
| Phragmites australis | Poaceae | Throughout Saudi Arabia | Perennial grass | High |
| Saccharum spontaneum | Poaceae | Throughout Saudi Arabia | Perennial grass | Low |
| Tamarix senegalensis | Tamaricaceae | Throughout Saudi Arabia (except high altitude and deep sands) | Shrub | Low |
Distribution, Impact and propagation
Species | Altitudinal variations (in meters) | Impact on Domestic herds
| Mode of dispersal
| Propagation
| |||
0- 500 | 501- 1000 | 1001- 2000 | 2001- 3000 | ||||
Alternanthera pungens |
| * | * | * | May cause skin problems to cattle | Seeds transported by shoes, water, wheels or animals | Seeds |
Amaranthus albus | * | * | Excessve quantity may cause problems to livestock | Wind, water, farm machinery | Seeds | ||
Amaranthus hybridus | * | * | * | No toxic effects reportted | Propagules transported through wind and water curents, soil transport | Seeds | |
Amaranthus spinosus | * | * | * | * | No toxic effects reportted | Wind, water, animals | Seeds |
Annona squamosa | * | No toxic effects reportted | Birds | Seeds | |||
Argemone mexicana | * | * | The yellow sap is Toxic | Wind and water | Seeds | ||
Argemone ochroleuca | * | * | The yellow sap is Toxic | Wind and water | Seeds | ||
Austrocylindropuntia subulata | * | * | Fruits edible. Spines hazardous to animals | Baboons, Through detached pads. | vegetative and seeds | ||
Atriplex suberecta | * | Unpalatable | Wind and water | Seeds | |||
Bidens aurea | * | Palatable | Wind , water, animals, shoes | Seeds | |||
Cenchrus echinatus | * | * | Achens are hazardous | Cloths, shoes, animals, plant dumping | Seeds | ||
Cenchrus gracillimus | * | * | Achens are hazardous | Cloths, shoes, animals, plant dumping | Seeds | ||
Cirsium vulgare | * | * | Unpalatable | wind, water, cloths | seeds | ||
Chenopodium atrovirens | * | Unpalatable | wind, water | Seeds | |||
Chenopodium desiccatum ssp. leptophylloides | * | Unpalatable | wind, water | Seeds | |||
Cuscuta campestris | * | * | Unpalatable | Stem parasite. Through infestation. | Seeds | ||
Cylindropuntia rosea | * | Unpalatable | Moving vehicles, shoes | Vegetative | |||
Datura ferox | * | Unpalatable Wind, water, cloths or through dumping sites | Seeds | ||||
Datura innoxia | * | unpalatable | Wind, water, cloths or through dumping sites | Seeds | |||
Datura metel | * | unpalatable | Wind, water, cloths or through dumping sites | Seeds | |||
Datura stramonium | * | unpalatable | Wind, water, cloths or through dumping sites | Seeds | |||
Dysphania ambrosioides | * | * | * | Unpalatable. It can cause dizziness, vomiting, convulsions and even death | Water | Seeds | |
Dysphania carinata | * | Unpalatable | Wind and water or from dumping site | Seeds | |||
Eclipta prostrata | * | * | Palatable. Also widely used as a medicinal plant | Water and wind | Seeds | ||
Encelia farinosa | * | Palatable | Wind | Seeds | |||
Erigeron bonariensis | * | * | * | * | Unpalatable | Wind and water, also As a contaminant of manure | Seeds |
Erigeron canadensis | * | * | Unpalatable | Wind and water, also as a contaminant of manure | Seeds | ||
Euphorbia cyathophora | * | unpalatable | as a contaminant of manure | Seeds | |||
Euphorbia heterophylla | * | unpalatable | As a contaminant of manure | Seeds | |||
Euphorbia hirta | * | * | * | * | Unpalatable. Toxic | Wind. Also as a contaminant of manure. | Seeds |
Euphorbia hypercifolia | * | Unpalatable. Toxic | Wind. Also as a contaminant of manure. | Seeds | |||
Euphorbia maculata | * | Unpalatable. Toxic | As a contaminant of manure. | Seeds | |||
Euphorbia prostrata Aiton | * | Unpalatable. Toxic | As a contaminant of manure. | Seeds | |||
Euphorbia tirucalli | * | * | Unpalatable. Toxic | Vegetative | Vegetative | ||
Flaveria trinervia | * | * | * | * | Unpalatable | Water | Seeds |
Galinsoga parviflora | * | No toxic effects reportted | Wind. Also as a contaminant of manure. | Seeds | |||
Heliotropium curassavicum | * | Toxic | Water | Seeds | |||
Ipomoea cairica | * | * | * | * | Unpalatable | Water | Seeds |
Ipomoea carnea ssp. fistulosa | * | Toxic | As a contaminant of manure | Seeds | |||
Jatropha curcas | * | * | Toxic | As a contaminant of manure | Seeds | ||
Lantana camara | * | * | * | Toxic | Water | Seeds | |
Leucaena leucocephala | * | * | Unpalatable | Wind and water | Seeds | ||
Lythrum hyssopifolia . | * | Unpalatable | Wind, water | Seeds | |||
Malvastrum coromandelianum | * | Unpalatable | Wind and water | Seeds | |||
Nicotiana glauca | * | * | Unpalatable | Wind and water | Seeds | ||
Operculina turpethum | * | Unpalatable | Wind and water | Seeds | |||
Opuntia ficus-indica | * | * | * | Fruits edible. Spines hazardous to animals | Baboons, Through detached pads. | vegetative and seeds | |
Opuntia stricta | * | * | * | Fruits edible. Spines hazardous to animals | Baboons, Through detached pads. | vegetative and seeds | |
Paspalum dilatatum | * | Unpalatable | Wind and water | Seeds | |||
Physalis peruviana | * | Palatable | Wind and water | Seeds | |||
Physalis stepelioides | * | Fruits edible | Birds, from dumping site | Seeds | |||
Potamogeton perfoliatus | * | Fruits edible | Birds, from dumping site | Seeds | |||
Neltuma juliflora | * | unpalatable | Water | vegetative and seeds | |||
Salsola kali | * | * | * | Fruit Palatable | Wind, from livestock excreta | Seeds | |
Senna occidentalis | * | * | seedlings palatable | Wind, water, from dumping site | Seeds | ||
Senna obtusifolia | * | Unpalatable | From dumping site | Seeds | |||
Sesuvium portulacastrum | * | Unpalatable | From dumping site | Seeds | |||
Sesuvium verrucosum | * | Unpalatable | From dumping site | Seeds | |||
Tagetes minuta | * | Unpalatable | From dumping site | Seeds | |||
Trianthema portulacastrum | * | * | Unpalatable | Wind, water | Seeds | ||
Tridax procumbens | * | * | Unpalatable | From dumping site | Seeds, also vegetatively | ||
Verbesina encelioides | * | * | * | Unpalatable | Wind, water, also from dumping site | Seeds | |
Xanthium spinosum | * | * | * | Unpalatable | Wind, water, from dumping site | Seeds | |
Impact on various ecological parameters
| Species | Ecological Impact | Dispersal ability | Adaptability to various habitats | Effects on multiple species | Effect on rare species | Effects on ecosystems | Action required for Score 15 and above |
| Low Impact (1); Moderate Impact (2); Severe Impact (3). | |||||||
| Alternanthera pungens | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Amaranthus albus | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Amaranthus hybridus | 1 | 2 | 1 | 1 | 1 | 1 | 11 |
| Amaranthus spinosus | 1 | 1 | 2 | 1 | 1 | 1 | 11 |
| Annona squamosa | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Argemone mexicana | 1 | 1 | 1 | 1 | 1 | 1 | 12 |
| Argemone ochroleuca | 3 | 3 | 1 | 2 | 3 | 2 | 22 |
| Austrocylindropuntia subulata | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Atriplex suberecta | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Bidens aurea | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Cenchrus echinatus | 2 | 2 | 1 | 1 | 1 | 1 | 12 |
| Cenchrus gracillimus | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Cirsium vulgare | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Chenopodium atrovirens | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Chenopodium desiccatum ssp. leptophylloides | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Cuscuta campestris | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Cylindropuntia rosea | 2 | 2 | 1 | 1 | 1 | 1 | 12 |
| Datura ferox | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Datura innoxia | 2 | 2 | 1 | 1 | 1 | 1 | 12 |
| Datura metel | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Datura stramonium | 2 | 1 | 1 | 1 | 1 | 1 | 11 |
| Dysphania ambrosioides | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Dysphania carinata | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Eclipta prostrata | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Encelia farinosa | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Erigeron bonariensis | 1 | 2 | 2 | 1 | 1 | 1 | 13 |
| Erigeron canadensis | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Euphorbia cyathophora | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Euphorbia heterophylla | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Euphorbia hirta | 2 | 1 | 1 | 1 | 1 | 1 | 12 |
| Euphorbia hypercifolia | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Euphorbia maculata | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Euphorbia prostrata Aiton | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Euphorbia tirucalli | 1 | 2 | 1 | 1 | 1 | 1 | 11 |
| Flaveria trinervia | 1 | 2 | 1 | 1 | 1 | 1 | 12 |
| Galinsoga parviflora | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Heliotropium curassavicum | 1 | 1 | 1 | 1 | 1 | 1 | 11 |
| Ipomoea cairica | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Ipomoea carnea ssp. fistulosa | 2 | 2 | 1 | 1 | 2 | 2 | 16 |
| Jatropha curcas | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Lantana camara | 2 | 1 | 1 | 2 | 1 | 1 | 14 |
| Leucaena leucocephala | 1 | 1 | 1 | 1 | 1 | 1 | 12 |
| Lythrum hyssopifolia . | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Malvastrum coromandelianum | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Nicotiana glauca | 3 | 3 | 2 | 1 | 1 | 2 | 22 |
| Operculina turpethum | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Opuntia ficus-indica | 2 | 2 | 2 | 2 | 2 | 2 | 21 |
| Opuntia stricta | 3 | 3 | 3 | 2 | 3 | 3 | 27 |
| Paspalum dilatatum | 3 | 3 | 3 | 1 | 1 | 3 | 24 |
| Physalis peruviana | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Physalis stepelioides | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Potamogeton perfoliatus | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Neltuma juliflora | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Salsola kali | 3 | 3 | 3 | 3 | 3 | 3 | 28 |
| Senna occidentalis | 2 | 2 | 1 | 1 | 1 | 2 | 17 |
| Senna obtusifolia | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Sesuvium portulacastrum | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Sesuvium verrucosum | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Tagetes minuta | 1 | 1 | 1 | 1 | 1 | 1 | 10 |
| Trianthema portulacastrum | 2 | 2 | 1 | 2 | 1 | 1 | 15 |
| Tridax procumbens | 2 | 1 | 1 | 1 | 1 | 1 | 11 |
| Verbesina encelioides | 1 | 1 | 1 | 1 | 1 | 1 | 12 |
| Xanthium spinosum | 2 | 2 | 1 | 2 | 1 | 1 | 14 |