Opuntia stricta, Bundula, Sri Lanka
This is an invasive species in Sri Lanka, and in particular in this location (Bundula). From Wikipedia:
"In Sri Lanka it has overgrown a 30 kilometer long coastal area between Hambantota and Yala National Park, especially in Bundala National Park, a Ramsar wetland site. It has overgrown several hundreds of hectares of sand dune areas and adjoining scrub forests and pasture lands. Some areas are so densely covered that they are completely inaccessible for humans and animals. The seeds are spread by macaque monkeys, and perhaps other animals and birds, that eat the large fruits. It is also spread by people cutting down the cactus but leaving the cuttings, which then re-sprout where they have fallen. No control measures have been carried out except some costly manual removal of about 10 hectares on the dunes near Bundala village. The cactus is due to invade Yala National Park."
''Opuntia stricta'' is a species of cactus from southern North America, Central America, the Caribbean, and northern South America. Common names include Erect Prickly Pear and Nopal Estricto .
It is an erect or sprawling shrub up to 2 m in height, producing lemon yellow flowers in the spring and summer, followed by purplish-red fruits.