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Biodiversity and sustainability
• ENS 201 explored social and economic facets of
sustainability
• ENS 202 explores the ecological facets of
sustainability
• Questions in this unit:
– How can we measure biodiversity?
– How is biodiversity calculated?
– How can biodiversity be put into policy?
What happens to ecosystems when we
alter their biodiversity? Do they provide
the same services? Do we jeopardize
the potential for sustainability?
Biodiversity and sustainability
• Many different ways to define sustainability – social,
economic, as well as biological
• Productivity and stability are two biological facets of
sustainability
– Productivity is the amount growth as measured in net
primary productivity
– Stability simply refers to its predictability over time
• How is species richness (number of species) related
to productivity and stability?
How is species richness related to
productivity and stability?
• Decrease in plant species numbers leads to
decrease in ecosystem stability in productivity
• Occurs independently of the factors driving
changes in biodiversity.
Biodiversity and sustainability
• More species is good, but there other ways to
measure biodiversity that are also informative
in regard to understanding the ecological
facets of sustainability
– Taxonomic diversity
– Alpha, beta, gamma diversity
– Genetic diversity
– Phenotypic diversity
– Phylogenetic diversity
– Functional diversity
– Response diversity
– Interaction diversity
– Landscape diversity
– Dark diversity
– Cryptic diversity
How to measure biodiversity
• Biodiversity can be described for different
taxonomic levels:
– Kingdom, Phylum, Class, Order, Family, Genus,
Species
– Thus one can measure species diversity, family
diversity, or class diversity
– Which is more diverse? 10 families consisting of
200 species vs 20 families containing 100 species?
•
Diversity can be described in terms of evenness and
richness
Low evenness:
elephants dominant
(Lower diversity)
Equal richnesssame number
of species (10)
High evenness
(Higher diversity)
• Diversity can be described as alpha, beta, and
gamma diversity
– Alpha (or local) diversity expresses the number of
species within a given habitat. It is the most common
way that diversity is employed
– Beta (or turnover) diversity expresses the difference,
or turnover, in species from one habitat to another.
– Gamma (or regional) diversity-total number of
species observed in all habitats within a geographic
area
Genetic diversity
• Genetic diversity
– A measure of one or several aspects of genomic
characteristics including
• DNA sequence of nucleotides (A,C, G, T)
– Types of DNA: nuclear, mitochondrial, ribosomal
• Genes
• Proteins
– A key point to realize here is that there are many
different ways to measure genetic characteristics.
Phylogenetic diversity
• Diversity arising
from differences in
species lineages
based on their
evolution
Functional diversity
Response diversity
Interaction diversity
• Characteristics of the network of linkages defined
by biotic interactions such as competition,
predation, parasitism, or facilitation, with other
species
Landscape diversity
• Number, relative abundance, and distribution
of different habitat types within a landscape
Relationships among different types of
diversity
Measuring biodiversity
• Use multiple kinds biodiversity – taxonomic,
phylogenetic, functional
• Aim to conserve specific biological values that
underlie biodiversity, not just the number of
species
• We have the responsibility to decide what
biological values to prioritize
• Vague generalizations of ‘biodiversity’ offer little
in the way of promoting and maintaining
sustainability
Measuring biodiversity
• Biodiversity is also the balance between speciation
and extinction
• Challenges to counting
– Taxonomic skills are necessary to find and identify new
species
– Fluidity of species concept
– Cryptic and dark biodiversity
– Speciation is ongoing
– Extinctions need to be verified
– Extinction debt
How many species?
• 5 - 9 million nonbacterial species
estimated
• Some estimates have
ranged up to 100 million
because of potential
insect diversity
• 1.5 million cataloged,
but many are only
descriptions or a
museum specimen
The challenges of counting
• Fluidity of species concept
• Cryptic and dark biodiversity
• Taxonomic skills are necessary to find and
identify new species
• Extinctions need to be verified
• Speciation is ongoing
• Extinction debt
• Current accounting or a long-term calculation
How to define a species?
• Difficult and fluid in
practice
• Apply a combination of
concepts
(morphological,
biological, evolutionary
relationships, genetics,
measures of fitness)
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Dark diversity
• All species in the
region that can
potentially inhabit a
defined set of local
ecological conditions.
The dark diversity for the grassland under
study also include species D and E as they
occur in the same habitat nearby.
Cryptic diversity
• Undetected or unnoticed
biodiversity: organisms are
too small, reclusive, isolated,
or similar in appearance to get
counted
• Human visual perception or
methods of detection cannot
adequately recognize extent
of biodiversity
• Identification aided by
phylogenetic methods
Environmental DNA (eDNA)
• A novel survey method to detect DNA in water or other
environmental samples for finding rare or missing species and
thereby improving future biodiversity inventories
New species get counted when
they are identified
• 30,000 to 40,000 taxonomists
worldwide
• 16,000 new species identified
per year
• However, overall there are
fewer species being described
per taxonomist, suggesting that
it may already be harder to
discover new species
Relatively large, conspicuous species are still
being discovered in remote or poorly studied
areas. Shown are (a) an undescribed jay
species from the Amazon basin, (b) a recently
discovered fruit bat and (c) monitor lizard
from the Philippines
Evolution and speciation in the
Anthropocene
• Speciation is the
evolutionary
process by which
new species arise
• Populations and
species have
begun to evolve,
diverge, hybridize
and even speciate
in new man-made
surroundings.
When do you conclude a species is extinct?
Difficult to verify extinction
• Of all the mammalian species thought to have
become extinct since the year 1500, about
one-third have at some stage been
rediscovered.
• How long should you continue to look?
• Where should you look for extinct species?
Extinction is not necessarily
easy to conclude. Sometimes
species thought to be extinct
are still present in small
isolated populations
Extinctions versus identification
How well will be able to identify
species on Earth if at the same
time some are going extinct?
Extinction versus identification
• If extinction rates are as high as 5% per
decade, then regardless of how many species
exist on Earth, more than half will be extinct
within 150 years, 2164
• At the rates considered more realistic (i.e.,
<1% per decade) the rate of species
description greatly outpaces extinction rates
whether there are 2 or 10 million species on
Earth.
Extinction debt
• Lock in of
future
extinction of
species due to
human
impacts that
occurred at
some earlier
point in time.
• Time delay
between
human impact
and extinction
Extinction debt
• More species persist following fragmentation and
diversity loss than predicted by species areas plots.
• Some species disappear (pay the debt) later
• This “debt” is the time-lagged response between
fragmentation and extinction of these species.