Johan A. Wahlberg, Swedish naturalist, entered the University of Uppsala in 1829, but soon left to study chemistry under a pharmacist. In 1831 he enrolled at the Institute of Forestry in Stockholm. The next year he accompanied the entomologist Professor C.H. Boheman on a collecting trip to Norway and during the next two years travelled in southern Sweden and parts of Germany in connection with forestry research. He graduated from the Institute of Forestry in 1833 or 1834, passed a surveying examination in May 1835, and studied agronomy for some time at the Degeberg Agricultural Institute. In September 1836 he was appointed as an engineer in the General Survey Office and taught physics, chemistry, natural history and agronomy in its school. In his spare time he collected and stuffed animals, being most interested in birds. In 1837 the Swedish consul in Cape Town, Jacob Letterstedt, asked the Swedish Academy of Sciences to provide financial support for a naturalist to visit South Africa to collect specimens for the Naturhistorika Riksmuseet (National Natural History Museum) in Stockholm. Wahlberg obtained the position and received a grant, though the amount was insufficient to meet his needs. In July 1838 he travelled to London to study museum collections, preparation techniques and the works of earlier travellers in South Africa, and met W.J. Burchell* and Dr Andrew Smith*.
Arriving in Cape Town on 2 February 1839 he collected in the vicinity for two months. Among others he met Baron C.F.H. von Ludwig*, C.L.P. Zeyher* and C.F. Ecklon*. On 15 May 1839 he and L.A.J. Delegorgue* sailed to Algoa Bay where he did some more collecting before sailing to Port Natal (now Durban) in the company of Delegorgue and C.F.F. Krauss*. For some time he stayed in a hut at Congella, among the Voortrekkers, collecting in the vicinity. Early in November 1839 he undertook a journey northwards to the Tugela River, on foot. Towards the end of the next month he slowly travelled to Pietermaritzburg, collecting all the way, and assisted the Voortrekker community during February and March 1840 in laying out the town. Returning to Port Natal he continued collecting in the neighbourhood and in May 1841 met the naturalist Dr W. Gueinzius*. In August 1841 and again in Septembe he visited Pietermaritzburg to make arrangements with the authorities there for an expedition into the Transvaal. His studies of particularly the birds of Natal were of fundamental importance, following the earlier work of Dr Andrew Smith*. During his extensive travels in the territory he built up a large collection that was later reported upon by Professor C.J. Sundevall, who described many new species from it.
In October 1841 Wahlberg set out for the Transvaal with an ox-waggon, accompanied by a young man named Willem Nel and two young Zulus. He crossed the Drakensberg at Bezuidenhout Pass, proceeded through the Free State and across the Vaal River to the site where Potchefstroom was being established. From there he went to the north of the Magaliesberg at Hartebeespoort, where he met Zeyher and Joseph Burke* on 17 November 1841. For the next six months he remained in the region between the Magaliesberg and the upper Limpopo River to collect and hunt. Returning by more or less the same route he reached Port Natal on 12 June 1842. In August that year he decided to go elephant hunting in Zululand and sell the ivory to cover expenses. Accompanied by Delegorgue and others he hunted and collected successfuly and met the Zulu king Mpande. Returning to Port Natal on 28 November he set out again, reaching the Tugela River in February 1843 and returned to Port Natal in April.
In June 1843 he set out for the Limpopo River again, with two ox-waggons and again accompanied by Willem Nel. From the Magaliesberg near present Rustenburg he travelled to the Matlapengberg, where he collected in September, and then eastwards to the Pilanesberg, where he met Delegorgue. Moving northwards he collected many mammals, birds and insects around the Witfonteinrand (south-west of present Thabazimbi) during October-November 1843, but then lost most of his oxen to tsetse-fly on the banks of the Crocodile River. He turned to elephant hunting to be able to buy new oxen and continued hunting and collecting all over the central Transvaal to as far east as the Elands River for many months. Returning to Port Natal in November 1844 he sailed for Cape Town in December. After an excursion to Saldanha Bay from January to March 1845 to collect sea birds he left for Sweden in May that year.
Wahlberg's collections included over 500 mammal skins; some 2500 birds of over 400 species, of which several were new; 480 reptiles and amphibians, most of them in alcohol; about 5000 species of insects; also fishes in alcohol, molluscs, and dried plants. The entire collection was sold to the Swedish Natural History Museum. Wahlberg returned to teach at the General Survey Office and shortly afterwards at the Institute of Forestry. In his spare time he described insects from his collection (1848, 1852, 1857-1858) and new species of birds in three papers in the Ofversigt (Survey) of the Swedish Academy of Sciences (1854, 1855, 1856). He also worked on an extensive manuscript titled Aves Africanae, containing over 1200 pages of descriptions and notes, mainly in Latin, on African bird life. This work remained incomplete and unpublished. His diary of his travels in South Africa was published as Anteckningsbok fran resorna i Sydafrika, 1838-1845 in 1855-1856.
In October 1853 Wahlberg left Sweden again, planning to explore southern Africa from the west coast, via Lake Ngami, to the Transvaal, probably inspired by the first description of the lake by David Livingstone*. He arrived in Cape Town in December and in March 1854 sailed for Walfish Bay in a ship which collected guano along the coast. This gave him an opportunity to study the bird populations on sevaral islands along the Namibian coast (and discover two new cormorants) before landing at Walfish Bay on 14 April 1854. From 10 May to 16 June he travelled to Rehoboth to buy oxen, but then remained at Rooibank, near present Walfish Bay, to wait for the rainy season. He collected mainly insects in the coastal Namib and along the Swakop River during this time. At the end of December he set out for Lake Ngami, probably following the route pioneered by C.J. Andersson* in 1853, via present Okahandja, Gobabis and Ghanzi. On this expedition he was accompanied by an assistant, Oscar Lindholm, whom he had engaged in Cape Town, and by the hunter and trader F.J. Green*. Reaching Lake Ngami in about April 1855 he and Green set out northwards in June to hunt and collect along the Taokhe and Okavango Rivers up to Libebe, near Andara. He returned to the lake in early November with much ivory and many specimens. Proceeding eastwards later that month he and Green hunted in the Kgwebe Hills and along the Botletle River until 6 March 1856 when Wahlberg was trampled to death by a wounded elephant that he was following. His collections and journals were sent to Sweden. Shortly after his death, before the news reached Sweden, he was elected a member of the Academy of Sciences.
Wahlberg's extensive collections were studied by various specialists and described in a number of important publications: Mammals by C.J. Sundevall (1845, 1847); reptiles and amphibians by A. Smith (1849) and W.C.H. Peters* (1862, 1869, 1870); birds by C.J. Sundevall (1850); Coleoptera by the entomologist with whom he had travelled to Norway, C.H. Boheman (1848, 1851, 1857, 1861) and by O.I. F?hraeus (1870-1872); Diptera by Loew (857, 1858, 1859, 1861); Lepidoptera by H.D.J. Wallengren (1856, 1857, 1865, 1872) and P.C. Zeller (1852) ; Hemiptera by St?l (1853, 1855, 1859, 1864-1866), Orthoptera by St?l (1855, 1856, 1858, 1871); molluscs by C.F.F. Krauss* (1848); crustaceans by Lov?n (1845, 1846); and the Natal fungi by E.M. Fries (1848). The number of new species described from his collections, mostly insects, probably exceeds 2000 (Brinck, 1955).
Wahlberg was rather short, but muscular, and unafraid of danger. He was an even-tempered but asocial man and although fond of children, he never married. His death was a considerable loss to science, as he was a born naturalist. However, the fact that he published little on his collections indicates his limitations as a scientist - he was primarily an excellent collector. More than 50 of the species he discovered were named after him, though many have since been renamed. Included are Wahlberg's eagle, Aquila wahlbergi; Wahlberg's epauletted fruit bat, Epomophorus wahlbergi; the Kalahari ground gecko, Colophus wahlbergii; numerous insects; Wahlberg's hunter snail Gulella wahlbergi; the tree genus Wahlbergia; and the plants Entada wahlbergii and Euphorbia wahlbergii.