Some structures and surfaces may block wildlife passage or provide a surface that does not allow wildlife to move across.
A study by Mateos-González et al. (2023) found that the number of garden crops (cabbage, kohlrabi, cauliflower, broccoli) were increased by 7.5 plants at harvest, when the crops were grown in a cold frame in a Czech republican area with European ground squirrels (Spermophilus citellus). Williams (1975) evaluated the effectiveness of a 30 cm aluminium band placed around palm trunks at 3.5 – 4.5 m off the ground to prevent rat damage to coconut in Fiji. The effect varied between trials and sites. In one site, damage was eliminated (RR = 0), while in another site two separate trials led to either a reduction in nut damage (RR = 0.65) or did not have any effect on reducing the risk of damage (RR = 1.1) in comparison to controls. The difference is assigned by the author to the height of the palms. The bands were ineffective for preventing damage on palms only 9–10 m high which had senile fronds that often bridged the aluminium bands and thereby allowed rats to bypass the band. On taller palms (over 15 m), the bands effectively prevented damage to nuts as these did not have fronds that allowed bypass.
