Geology Reference
In-Depth Information
In another series of experiments, scientists created artificial ecological communities
by seeding glass bottles containing water and nutrients with differing diverse communit-
ies of bacteria and their larger protist predators. In these experiments, greater diversity
led to less variability in the flow of carbon dioxide in and out of the community. The
message here is that more diverse real-world communities could provide more predict-
able and dependable emergent ecological functions, such as carbon capture and storage.
Recent mathematical modelling has also contributed to the new understanding of the
relationship between biodiversity and ecological health. We now know from detailed
fieldwork that ecological communities are replete with weak interactions, with many
predators focusing on eating a few individuals from a fairly wide range of species.
Models that take account of these insights show that virtual communities with realistic
feeding relationships and abundant weak interactions are more stable than previously
thought possible. Another group of mathematical models known as 'community as-
sembly models' work by creating a pool of virtual plants, herbivores and carnivores,
each with its own body size and preferences for food and space. One species at time is
placed in an 'arena' where it interacts with other species that are already present. After
a while, an astonishing thing happens—persistent communities self-assemble with a fi-
nal membership of about 15 species. As the number of species builds up, it becomes
harder and harder for an invader to find a toehold in the nexus of interacting species.
Communities that have existed for longer are harder to invade than newly established
ones, strongly suggesting that communities develop an emergent protective network that
becomes more effective as the community matures. Amazingly, the challenge for an in-
vader lies with the community as whole. In a mature, well-connected community, an
inferior competitor has a better chance of surviving an invasion from a superior compet-
itor than it would as a member of a less well connected community.
It is astonishing that these sorts of true-to-life emergent properties should appear in
mere mathematical communities. All the research we've looked at so far, from field,
laboratory and computer modelling, tends to support Clements' idea that ecological
communities can indeed be thought of a superorganisms which function more smoothly
and predictably as their biodiversity increases. But perhaps Clements and Tansley were
both right after all; perhaps each had seen different sides of the same coin. If so, there
is nothing inevitable about which species will colonise a bare patch of land, or indeed
nothing inevitable about how a particular succession will progress (Tansley), but as soon
as the species in a given place begin to web themselves together, the whole community
becomes a superorganism with powerful emergent properties (Clements).
This implies that the plant community is an animate entity which experiences its sur-
roundings as a single being capable of responding to threats and dangers somewhat like
our own sensing bodies. In Clements' ideas, as in those of Lovelock, there is a strong
