Biodiversity is the variety of life, including variation among genes, species and functional traits. It is often measured as:
• richness is a measure of the number of unique life forms
• evenness is a measure of the equitability among life forms
• heterogeneity is the dissimilarity among life forms
Ecosystem functions are ecological processes that control the fluxes of energy, nutrients and organic matter through an environment.
Examples include: primary production, nutrient cycling, and decomposition
Ecosystem services are the suite of benefits that ecosystems provide to humanity. There are two major types of ecosystem services:
• Provisioning services involve the production of renewable resources (e.g. food, wood, fresh water).
• Regulating services are those th at lessen environmental change (e.g. climate regulation, pest/disease control).
1. What are Ecosystem Services?
Ecosystem Services are all the processes through which natural ecosystems and the biodiversity they contain help sustain huma n life
on the earth.
• Maintenance of biodiversity
• Nutrient cycling
We should also recognize ecosystem dis-services. These are activities that reduce productivity:
• Habitat loss and degradation
• Nutrient runoff
• Soil erosion
• Pesticide application
Biodiversity is a term used to describe the diversity of important ecological entities that includes genes, species, communities.
• As the human population has grown, and we have cut, plowed, drained, and dammed, we have destro yed the habitat of many
• These changes have given rise to a biodiversity crisis.
• The Red List of Threatened Species, compiled by the World Conservation Union, lists 16,118 species as threatened with
Protecting biodiversity is criticall y important on many levels:
• We use hundreds of domesticated and wild species for food, fuel, fiber, medicines, and building materials.
• We are dependent on ecosystem services
Introduction of non-native/ invasive species
• The movement and introduction of spe cies to all parts of the globe has increased over the last century.
• The range expansion of some species has coincided with range contraction of many native species.
• The greatest “losers” among native species tend to be specialists with adaptations that re sulted from evolution in a particular
• The “winners” tend to be generalists with less stringent habitat requirements.
Threat to Biodiversity
• The ecological footprint of humanity on Earth is large and rapidly increasing.
• 83% of the land surface has b een modified in some way.
• Humans are now appropriating 10% –55% of Earth’s primary production and has appropriated 98% of the area where wheat,
corn, or rice can be grown.
• This human footprint is by far the most important factor contributing to global decl ines in biodiversity. (Habitat Loss Results
from a Growing Human Footprint)
Thus, addressing humans’ effects is central to conservation work:
• Habitat degradation - changes that reduce quality of the habitat for many, but not all, species.
• Habitat fragmentation - breaking up of continuous habitat into habitat patches amid a human -dominated landscape.
• Habitat loss - conversion of an ecosystem to another use.
• The Atlantic Forest of Brazil has suffered large losses. Its location coincides with 70% of Brazil’s human population.
• More than 92% has been cleared for agriculture and urban development, and what remains is highly fragmented.
• This moist tropical forest has many endemic species, many threatened with extinction.
• Habitat loss to motorways, airpor t runways, urban development etc.
• Habitat degradation is even more widespread than habitat loss.
• It can have many causes, such as overgrazing, vegetation harvesting, agriculture, and pollution.
• Sand dune habitat in the Sinai Peninsula had been degraded b y grazing and agriculture.
• Exotic species or Invasive species are those that have not originated in that area, but have arrived either naturally or by
human. They often sustain growing populations and have large effects on communities.
• Indigenous species are those that live naturally in that area
• Endemic species are those that are both indigenous and occur nowhere else
• Of particular concern are invasive species that impact native endangered species.
• Eurasian Zebra mussels have had negative impacts o n the freshwater mussel species of North America (p391).
• Introduced into the Great Lakes in 1980s, rapidly spread into the St. Lawrence and Mississippi basin.
• North America has 297 species of mussels, 1/3 of the world’s total.
• Many species are endemic, and rare, and were already threatened by poor water quality and habitat loss.
• The Nile perch was introduced into Lake Victoria in Africa in the early 1960s.
• After about 15 years, population size increased, as the native endemic cichlid species decline d. As many as 200 cichlid
species may have gone extinct.
• Before the introduction, cichlids made up 80% of the biomass in the lake; the Nile perch now accounts for 80% of the
BIODIVERSITY LOSS – some other considerations
I. Some species have evolved tight coevolved links to other species
• Hibiscadelphus plants and honeyeaters in Hawaii
• Calvaria trees and Dodo on the island of Mauritius
II. Protection of some species requires maintaining the essential components of the food web
• A Keystone Species is a species (usually having a low frequency) in a community whose removal has strong effects on
community diversity and composition; they are often top predators.
• Ex. Sea stars
III. Exotic predators
• excessive predation occurs when endemic species have e volved without predators – they have no antipredator behaviour.
• Ex. Black Stilts that are native to New Zealand are endangered due to exotic species (predators) such as ferrets and stoats
IV. Range decline:
• ex Food supply collapses over large areas when bamboo flowers synchronously at periods of several decades.
• Conservation requires reserves of bamboo over very large spatial scales
V. Effect of biotic invasions on humans
1. The Black death of Europe – Bubonic plague
spread by the brown rat in late 1300s – 50% mortality
2. Influenza pandemic 1918 at end of World War 1
killed about 100 million worldwide (now - H1N1 “swine” flu, bird flu, SARS, HIV -AIDS etc.)
3. Potato fungus in Europe in mid 1800s – caused the
emigration of Irish to North Amer ica
VI. Reasons for invasion success
1. Filled an empty niche
ex. Sea Lamprey (Petromyzon) – primitive fish, parasitic on other fish
• Lives in Atlantic, breeds in rivers.
• In St Lawrence river below Niagara Falls Are$Humans$Reducing$the$Ecosystem$Services$on$which$we$Depend?$
• 1829 Welland ship canal
• 1930 Entered Lake Eyrie
• 1946 Entered Lake Superior
• Caused the collapse of the fishery on lake trout
2. Species filling new niche
• open grasslands, created by humans. Previously adapted to this whereas indigenous species are not.
• Ex. European Starling – deliberate introduction
• 1891; 80 pairs released in Central Park, New York
• Spread from there westwards
• 1954; reached the west coast
3. All superior competitors
Fire ant (Argentine ant) – Iridomyrmex humilis
• 1891 into New Orleans from Argentina in shipping
• Very aggressive and displaced local indigenous ants
• In 50 years covered all of southern USA
• Venezuelan Cane toads, introduced to Hawaii, then Australia to eat pests of sugar cane in 1930s. Has now spread through
northern Australia eating other frogs and insects.
• African bees are very aggressive. In 1955 they were brought by bee -breeders to Brazil from Africa to cross with European
Domestic bees. Accidentally released and spread over South America and southern North America.
4. Successful spread due to absence of natural enemies
European Spruce sawfly (wasp)
1930; introduced in timber in Maritime provinces of Canada
1937; covered 10,000 km 2
• Absence of natural parasitoids (parasites of insects)
• Attacks pines and spruce (Norway, white, and black)
• Controlled by introduction of a viral disease
VII. Plant invaders
• will invade all continents if they have a competitive advantage
• Knapweed in British Columbia takes over grazing land and makes it unusable
Biodiversity – Ecosystem Function (BEF)
The balance of evidence that has accrued over the last 20 years leads to the following conclusions on how biodiversity loss impacts
functioning of ecosystems (BEF).
1. biodiversity loss reduces the efficiency by which ecological communities capture biologically essentia l resources, produce
biomass, decompose and recycle biologically essential nutrients (Fig. 1).
2. biodiversity increases the stability of ecosystem functions through time.
3. The impact of biodiversity on any single ecosystem process is nonlinear and saturating, such that change accelerates as
biodiversity loss increases.
4. Diverse communities are more productive because they contain key species that have a large influence on productivity, and
differences in functional traits among organisms increase total resource capture.
5. Loss of diversity across trophic levels has the potential to influence ecosystem functions even more strongly than diversity
loss within trophic levels.
Biodiversity – Ecosystem Services (BES)
There is now sufficient evidence that biodiversity p er se either directly influences (experimental evidence) or is strongly
correlated with (observational evidence) certain provisioning and regulating services:
1. For many ecosystem services, the evidence for effects of biodiversity is mixed, and the contribut ion of biodiversity per se to
the service is less well defined.
2. For many services, there are insufficient data to evaluate the relationship between biodiversity and the service.
3. For a small number of ecosystem services, current evidence for the impact of b iodiversity runs counter to expectations.
2. What is nutrient cycling?
Nutrient cycling: the movement of nutrients within and between ecosystems.
A. Biogeochemical cycles:
• Exchange within an ecosystem
• To determine nutrient inputs and losses, we must define ecosystem boundaries. Are$Humans$Reducing$the$Ecosystem$Services$on$which$we$Depend?$
• For terrestrial ecosystems, a single drainage basin is often used, called a catchment or watershed—the terrestrial area that is
drained by a single stream.
A few major general principles:
1. Nutrient cycling is never perfect i.e. always inputs and outputs
2. Inputs and outputs are small in comparison to amounts held in biomass and recycled i.e. relatively 'tight' cycling is the norm
3. Disturbances (e.g. deforestation) often uncouples cycling