Agriculture Reference
In-Depth Information
comes, and the harder it becomes for a tree seed to find a place in the turf to get established.
That is why mowing a lawn every few weeks keeps it healthy.
Because of this survival strategy, grassland as a whole is highly edible, but only to ru-
minants and other fibre-eating herbivores; humans are only adapted to eating fruits and
seeds, which both trees and grass produce. However, we can eat the animals that eat the
grass, albeit at a low level of efficiency, and thus the whole of a field of grass is potentially
edible.
A tree, by contrast, survives by growing to the stage where its trunk and boughs are too
tough to eat. Except for the bark, its Achilles heel, a mature tree trunk is a triumph of in-
edibility, eaten by nothing until the tree sickens or dies. Up in the canopy there is often
food, but not all creatures can get there to eat it. Birds, insects, squirrels, monkeys and fruit
bats are welcome to dine on the flowers, nuts and fruit, and often that helps to spread the
species. But humans have difficulty getting up there, and, more importantly for the tree,
ruminants can't usually get up there either. A herd of tree climbing goats might polish off
all the leaves of a tree in no time at all, and repeated attacks could leave an adolescent tree
it advantageous to crop the leaves to feed to animals in winter in the form of dried faggots,
but probably only when the small branches were useful for fuel as well. For the most part
we have found it easier to make hay or silage.
The result is that landscapes dominated by grass normally offer humans more food than
landscapes dominated by trees, both in regard to the accessibility of the seeds and the avail-
ability of meat. It is therefore not surprising that agricultural civilization evolved in the dry-
er areas of Europe and the Middle East, where trees were handicapped by a lack of water
to support their superior bulk; and that early agriculturalists chose to improve and domest-
icate grass seed rather than tree seed, both because it was more accessible, and because all
of the rest of the plant could be eaten by livestock.
These are the ecological dynamics that explain why our diet consists primarily of grass,
and why a succession of commentators have come out with epigrams like 'the basis of hu-
man proliferation is not our own seed, but the seed of grasses' and 'grasses are the greatest
fossil fuels, was woodland whose inedible infrastructure provided fuel, fibre and building
material, but this remained secondary to the need to eat.
Grass's strategy of competing through edibility has proved spectacularly successful, not
because herbivores have been particularly effective at keeping the tree population down,
but because human predators have intervened on their side. There is a mutual dependence
between predators, prey and fodder plants, whereas trees are have made themselves so un-
palatable that they don't have many allies. As a result the frontier that separates forest from
grassland has receded to the point that the planet's ecological equilibrium appears to be
