Scottish Natural Heritage has released figures showing that 78.8% of natural features on protected sites, from birds and bogs to plants and fossils, are in favourable condition, a slight rise compared with last year.
But the report says there has been a marked increase in the proportion of natural features which are being adversely affected by invasive species, "so much so that this is now the main pressure on natural features; 19.3% of all negative pressures identified are related to the effects of invasive species," it adds. "This includes both non-native species, such as rhododendron in woodlands, and native species, such as whins (gorse) encroaching on to grassland habitats."
Meanwhile, more than 90 alien species have been identified in British and Irish waters, with 17 established in Scotland.
The Firth of Clyde Forum, in partnership with SNH, have created a pocket-sized identification guide which encourages people to take a photo of anything unusual and send the pictures to a website where an expert will identify it. If the species is identified as being of high concern, then it will automatically be prioritised for action by the authorities.
Species such as invasive carpet sea squirts like Didemnum vexillum, a fast-growing animal which smothers underwater plants and animals, is already present in Scotland. It was first reported in the UK in 2008 and has been found in several sites in the Clyde.