Your garden will be attacked by various predators during the growing season, not least slugs and caterpillars. You never seem to be fully able to get rid of them. However, gardeners have helpful allies which eat the predatory species.
The first of your allies is the lady bird. While it appears to be such an attractive insect it is a ruthless predator that devours aphids, which feed upon the leaves of several varieties of plant.
Another ally are tits. Members of the tit family feed upon insects and their larvae, such as sawfly and codling moth, which do so much damage to fruit in Spring. To encourage blue tits, place nesting boxes nailed to trees at places in your garden and ensure that if they are inhabited you do not disturb them. They are particularly important in spring when the larvae are feeding.
Hedgehogs are another useful predator, especially as they attack at night. Though a much loved creature the hedgehog is a predatory beast that feeds on a variety of insects. It is particularly good for feeding on slugs and snails, especially as they are active at night, when the hedgehog is hunting. It is important that if you want to encourage hedgehogs you do not put down slug pellets, as they poison the slugs, which when eaten by the hedgehogs cause them to be poisoned. An old gardener told me once of his distress when he heard the wails of a hedgehog poisoned by eating slugs that had eaten toxic pellets. There are organic slug pellets which work not by poison but by gumming up the slug's digestion, and they are aceptable, but the poisonous ones should never be used.Hedgehogs can be encouraged by having a wild area where plies of leaves are left for them to nest in, and there are several hedgehog houses which can be made using designs on the internet.
A pond is a useful addition to an organic garden. Try to get some frogs in it. Frogs will be drawn to the pond where they are hatched, so get some frog spawn and place it in the pond. This will lead them to return year on year. Frogs, though, do not live in the pond, only tadpoles do, as the frog spends much of its time hiding in grass and leaves. They like to return to the pond at times to breed and to keep themselves wet. Compost heaps are popular with frogs, as they are likely to be warm, moist and have a large insect fauna, inclusing slugs and snails. A neighbour of mine took up a large tarpaulin a few years and found a large, apparently well-fed frog and several half eaten slugs. This indicates that frogs need a comfortable and sheltered place to stay. As slugs are also attracted to sheltered places, the frog had found a very nice spot indeed.
Another ally is a duck. Ducks must have a pond to swim in, but if you have a pond then they area possibility. Ducks can be allowed to wander round the plot, where they forage for slugs. To keep them you need adequate housing safe from foxes and a pond. However, when you have ponds full attention to health and safety issues is a must, especially when there are children around.
Chickens can be helpful. They are known as a chicken tractor, as they can peck between the rows of vegetables destroying slugs. They need housing sufficiently strong to keep foxes out and they need proper care and feeding, as they cannot rely only on what they peck from a garden.