Individual study: Passive Recovery of Vegetation after Herbivore Eradication on Santa Cruz Island, California
Beltran R.S., Kreidler N., Van V.D.H., Morrison S.A., Zavaleta E.S., Newton K., Tershy B.R. & Croll D.A. (2014) Passive Recovery of Vegetation after Herbivore Eradication on Santa Cruz Island, California. Restoration Ecology, 22, 790-797
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Reduce numbers of large herbivores
A before-and-after trial from 1980 to 2012 in coastal shrubland on Santa Cruz island, USA (Beltran et al. 2014) found that reducing grazing pressure by removing feral sheep, cattle, and horses increased shrub cover and reduced grass cover. After 20 years, cover of woody species was higher after the removal of sheep, cattle, and horses (24%) than before removal (1%), but cover of herbaceous plants did not differ significantly (after: 66%, before: 60%). Cover of bare ground was lower after the removal of sheep, cattle, and horses (9%) than before removal (39%). Sheep, cattle, and horses were removed from the island between 1981 and 1989. In 1980 and 2012 twenty 30 m transects were used to survey vegetation. Every 1 m along the transects the vegetation type was identified and cover was estimated.
(Summarised by Phil Martin)
Other biodiversity: Exclude grazers
A before-and-after study in 1980–2012 on Santa Cruz Island, California, USA, found that the cover of woody vegetation increased and the cover of exotic grasses and bare ground decreased following the eradication of feral sheep from the island in 1984. Plants: Cover of woody vegetation estimated using transects increased from 1980 to 2012 (1% vs 24%), whilst bare ground decreased (40% vs 9%) and the cover of herbaceous vegetation did not change (60% vs 67%). Woody overstory plant cover (estimated from photographs) increased from 27% in 1979/1980 to 53% in 2009. Total woody vegetation cover across the island (estimated from aerial photos) increased from 26% to 77% between 1985 and 2005. Cover of non-native grasses and bare ground decreased (grasses: 68% vs 21%; bare ground: 7% vs 2%). Methods: Vegetation was monitored using transects (1980, 2012), photographs (1979/1980, 2009), and aerial photographs (1985, 2005). Before eradication, sheep had grazed the island since around 1850, at a density of approximately 2 sheep/ha (in 1980).