He is best known for his work A description of the genus Pinus, issued in several parts 1803–1824, a sumptuously illustrated folio volume detailing all of the conifers then known.

Lambert acquired a number of significant herbarium collections including those of Johann Reinhold Forster, Archibald Menzies and Henry de Ponthieu.

[1][5] In 1791, Lambert was elected to the Royal Society of London for Improving Natural Knowledge and Joseph Banks made him a member of its Council in 1810.

[6] "He was a friend and correspondent of Sir Joseph Banks, and took a great interest in the botanical and zoological discoveries emerging from New Holland in the late 18th and early 19th centuries, as they were transmitted back to London, whether as living or dead specimens, as seeds, or as drawings.

"[7] Lambert is honoured in the scientific name of the Sugar Pine (Pinus lambertiana), the genus Lambertia, and the variegated fairywren (Malurus lamberti).