German naturalist. Dieffenbach made a brief but pioneering scientific exploration of New Zealand in 1839-1841, being the first trained scientist to work in the country. Born at Giessen, Diffenbach began studying medicine at the city's university in 1828, but after joining the agitation for political reform at that time was forced to flee the country, standing accused of subversive activities. He moved to Zurich and again began studying for a degree in medicine. Yet once more he found himself caught up in trouble, and was imprisoned for more than two months, including a week for duelling. He was expelled from the country for political activities in 1836. Fortunately for Dieffenbach he had earned his MD degree the preceding year. Arriving in London in 1837 (where he was known as Ernest) he built a reputation for himself as a scientist, contributing to journals and becoming acquainted with Charles Darwin, Charles Lyell and Richard Owen.

In 1839 Dieffenbach was appointed as a naturalist by the New Zealand Company, sailing there in May that year to assess sites suitable for settlement. He made surveys of the Marlborough Sounds, the Hutt Valley, the west coast of the North Island and its central volcanic regions, making charts, measuring tides and temperatures and collecting flora, fauna and geological items, which were dispatched to Kew and the British Museum. He and James Heberley were the first Europeans to ascend Mount Taranaki (Egmont), in December 1839, on which journey Dieffenbach found the plants Dracophyllum rosmarinifolium and Solidago arborescens.

In mid-1841 Dieffenbach and his party stayed with the missionary couple Thomas and Anne Chapman at Lake Rotorua. He also made a five-week visit to the Chatham Islands in May - June 1840, and spent time in New South Wales, Australia, later that year. E.J. Godley's biographical notes on Dieffenbach give a chronological account of his movements (see the New Zealand Botanical Society Newsletter 76, 2004).

Dieffenbach disagreed with others at the New Zealand Company about some of its reports, and did like not many of the settlers he met, calling them a "race of shopkeepers" proud of their ignorance of the native culture. He nevertheless asked for an extension to his contract in 1841, that he might stay to complete a full scientific survey of the islands. Unsuccessful in his petition, he was back in England by October 1841, where he published a report on the Chatham Islands in the New Zealand Journal. Two years later his Travels in New Zealand appeared, describing the country and the Maori people. In particular he made a plea for the Maori culture to be protected as European colonisation and its individualistic ways encroached more and more on their land.

In England Dieffenbach followed a career as a translator and scientist, attempting in vain to find a passage back to New Zealand. He moved back to Giessen in 1848, where he became professor of geology at the university and director of the geological museum. After marrying Katharina Reuning in 1851, he enjoyed only four years of their life together before dying of typhus, leaving behind their two daughters. In his last years he had translated Darwin's Journal of Researches into German. The plant genus Dieffenbachia Schott commemorates him. The flightless bird, Dieffenbach's Rail (Gallirallus dieffenbachia), now extinct, was also named in his honour.

Sources:
E.J. Godley, 2004, "Biographical Notes (54): John Carl Ernest Dieffenbach (1811-1855)", New Zealand Botanical Society Newsletter, 76(June): 31-35
D. McLean, "Dieffenbach, Johann Karl Ernst 1811-1855", Dictionary of New Zealand Biography, updated 22 June 2007:
http://www.dnzb.govt.nz/, accessed 20 July 2010.