Some eucalyptus species have attracted attention from horticulturists, global development researchers, and environmentalists because of desirable traits such as being fast-growing sources of wood, producing oil that can be used for cleaning and as a natural insecticide, or an ability to be used to drain swamps and thereby reduce the risk of malaria. Eucalyptus oil finds many uses like in fuels, fragrances, insect repellance and antimicrobial activity. Eucalyptus trees show allelopathic effects; they release compounds which inhibit other plant species from growing nearby. Outside their natural ranges, eucalypts are both lauded for their beneficial economic impact on poor populations and criticised for being "water-guzzling" aliens, leading to controversy over their total impact.