The London gardeners' forum sought to identify how gardeners could improve the sustainability of their managed landscapes.
Royal Parks head of ecology Nigel Reeve suggested planting natives instead of exotics and cultivars. He said: "We're not conserving natural habitats, we're using this as gardening." He advocated low-frequency grass cutting and leaving uncut wildlife refuges in winter. This has led to heather returning to Kensington Gardens and yellow ant hills at Bushy Park. He added that using cows and deer rather than mowers helped biodiversity.
Royal Parks uses specialist contractors to monitor pond water. Gardeners leave decaying wood and "monolith" trees to encourage insects, only allow dogs on leads in skylark areas and run bird surveys.
Ian Wright, National Trust gardens adviser for Devon and Cornwall and the trust's lead adviser on Phytophthora, spoke about putting in "barriers" to help bio-security.
He said gardeners' awareness was rising because of Phytophthora and citrus longhorn beetle threats. A Plant Network Conference in Sheffield on collective responsibility towards pests, diseases and invasive plants further highlighted the issues this week.
Natural England London regional biodiversity co-ordinator Nick White said the 1992 Rio UN convention, which aimed to end EU biodiversity loss by 2010, had not succeeded. But he added that new targets to be set in Nagoya this October were likely to be more realistic.