MODULE 021131: ECOLOGYLearning Objectives: Lecture 1

? Ecology covers a hierarchy of levels of organisation, from individual to biosphere

? There are distinctive (emergent) properties of ecological systems at each of these scales that can only be understood by studying them at the appropriate scale: a strictly reductionist approach is invalid

? If an ecological problem is to be successfully resolved, it must be studied at all appropriate scales

Ecology as a hierarchy

• Molecule cell• Organism• Population• Community• Ecosystem• Landscape, biome, biosphere

At the level of the individual organism:

• Phenomena include animal behaviour, ecophysiology

• Applications are in species conservation, land management

Large blue butterfly Maculineaarion: unique life-history is the key to its conservation

Spring gentian Gentiana verna: found only in a few places in Britain, and sensitive both to soil conditions and grazing

Habitat of G. verna in Upper Teesdale, County Durham. The fence controls grazing and allows abundant flowering.

The reservoir in the background flooded over half the habitat of this rare species

The lichen Hypogymnia physodes: lichens are highly sensitive to air pollution and are rare in urban areas.

Their sensitivity can be used as an index of pollution intensity

Derelict coal-mine waste in the central Lancashire coalfield: grass growth is poor and restricted to gulleys where water collects

Derelict land encourages other low-value uses of land and depresses the local economy

Plants cannot grow on the waste, due to extreme deficiency of mineral nutrients such as phosphate

Sown grass seed soon dies of drought as a result of inadequate growth of their root systems

Adding ground limestone (CaCO3; to raise the soil pH) and fertilisers allows grass growth on otherwise barren sites No

limestoneLimestone added

The individual plots received different combinations of N, P and K fertilisers

At the population level

• Phenomena: population dynamics, extinction, competition, predation

• Applications: invasions, pest control, biological control, conservation management

an introduced species that has escaped from gardens and now dominates in waterside habitats

produces huge numbers of seeds and can swamp

all competitor species

Himalayan balsam Impatiens glandulifera

Touch-me-not balsam Impatiens noli-me-tangere is a closely related native species that is now very rare in Britain.

Why is one species an invasive weed and the other rare and threatened?

Invasive species can have large economic consequences

Patterson’s curse Echium plantagineumcan take over entire fields in Western Australia

Australian vegetation is especially prone to invasions: almost all the species in this scene are introduced from either South Africa or the Mediterranean

Species that are well controlled by natural enemies in their native range, such as this prickly pear Opuntia in South America, can become damaging weeds in another country: here Australia.

Prickly pear was eventually controlled by introducing a moth Cactoblastiscactorum whose caterpillars ate it

Community level:

• Phenomena: biodiversity, succession

• Applications: habitat management, biodiversity conservation

What is the appropriate way to manage biodiverse habitats such as chalk grassland?

Species-rich grassland is maintained by grazing

when grazing is removed, coarse grasses dominate

Tropical wet forests are the most diverse habitats we know:

why are they able to support so many species?

Ecosystem level:

• Phenomena: nutrient and material cycles, stability, ecosystem services

• Applications: pollutant transport, eutrophication, acid rain, sustainable agriculture

A polluted ditch threatens an important wildlife habitat: Askham Bog, near York

Higher levels: landscape, biome, biosphere

• Phenomena: dispersal,

• Applications: global change, sustainability

Soil erosion can have catastrophic consequences for the environment:

a dust-storm in Mexico

Long-distance transport of eroded soil connects distant ecosystems

Reductionism

• can one explain higher levels or organisation by understanding the lower levels?

• does the study of the natural world ultimately reduce to physics?

• emergent properties