Born in Djakarta, Indonesia, Kleinpaste was educated in The Netherlands, and then studied plant sciences at Wageningen University, eventually earning a degree in silviculture.

After immigrating to New Zealand in 1978, he worked in various environmental jobs before settling down to 14 years in the Ministry of Agriculture and Fisheries (MAF).

In 1987 he started a talkback radio show (Ruud's Awakening) in which he offers environmentally friendly horticultural tips to gardeners.

These include promoting environmentally friendly agricultural techniques, the protection of endangered native NZ birds, and, most famously, the understanding and appreciation of insects, spiders, and other terrestrial arthropods.

In the 2018 New Year Honours, Kleinpaste was appointed an honorary Member of the New Zealand Order of Merit for services to entomology, conservation and entertainment.