ecosystems Flashcards
(15 cards)
What is biodiversity?
Biodiversity can be described as the variability among living organisms, within species and across species, encapsulating the diversity of life from the level of the gene to that of the ecosystem. It is a property of nature underpinning the resilience and adaptive capacity of systems at every level of biological organisation.
Why is it important to clarify the definition of biodiversity with respect to human populations?
It is important to prevent the perpetuation of false narratives stating that biodiversity maintenance negatively impacts quality of life, and to promote effective conservation. It is also important to accurately define biodiversity to enable accurate measurement and monitoring of ecosystem diversity.
What are some different measures of biodiversity?
There are several forms of variability within and among ecosystem components - e.g. species richness (the number of different species represented across an ecosystem), species heterogeneity (the degree of difference between groups of species represented across an ecosystem), species abundance (the number of individuals of a single species across an ecosystem) and species evenness (the distribution of individuals of different species across an ecosystem, i.e. high evenness means there is a fairly equal number of individuals of each species).
What are the differences between alpha, beta and gamma diversity?
Alpha diversity refers to species richness within a given area. Beta diversity measures differences in species composition between different areas; i.e. species turnover among sites. Gamma diversity represents the total species diversity across a number of different ecosystems within a region.
What is the latitudinal diversity gradient?
The latitudinal diversity gradient reflects a pattern observed across marine and freshwater ecosystems, wherein abundance of vertebrate species per unit area is concentrated near to the equator and diminished near the poles. This gradient is mirrored by the elevational diversity gradient, wherein diversity peaks at mid-elevations for many taxa.
Are all taxa uniformly biodiverse?
No. Some clades are significantly more diverse. For example, there are between five and six hundred species of Lake Malawi cichlids - and only five species of Lake Malawi tigerfish. Most higher taxa contain few subordinate taxa, whilst a few lineages contain numerous. Evolutionary success is concentrated within a few lineages.
Can the evolutionary success of a taxon be correlated with age?
No. The diversification rate of a clade is unrelated to the age of that lineage, with no ubiquitous temporal pattern.
What are some hypotheses for geographical variations in biodiversity?
The area hypothesis posits that the larger land area of the southern hemisphere provides more niches and thus more opportunities for diversification. The energy hypothesis posits that the more consistently high levels of solar radiation to which the southern hemisphere is exposed stimulates higher net primary productivity, producing more resources and niches for specialisation. The higher ambient temperature hypothesis holds that higher temperatures are associated with faster metabolism - and with higher mutation rates, resulting in faster rates of evolution/speciation. Additionally, some hypothesise that biodiversity begets biodiversity - with the presence of more species entailing more complex species interactions, resulting in more frequent coevolution and thus speciation.
What are some hypotheses for phylogenetic variation in biodiversity?
Some hypothesise that certain life-history traits predispose lineages to radiation (e.g. low levels of dispersal). Biogeographical factors may isolate populations from one another - e.g. the emergence of a geographical barrier might slow/halt gene flow between populations, resulting in eventual divergence and speciation. For example, the rise of the Andes in Amazonia induced the reorientation of river systems, isolating populations from one another and generating novel habitats. Isolated populations with low dispersal rates were more likely to diverge and speciate as a consequence.
What is an example of the cultural value of biodiversity?
The Whanganui River in New Zealand is of great cultural significance to the indigenous Maori people (Te awa tupua). It is considered the source of both spiritual and physical sustenance for the Whanganui iwi tribe and constitutes a taonga (treasure) within their culture. The river was granted legal personhood thirteen years ago and is now subject to human rights considerations and legal representation, preserving the broadleaf and podocarp forest and numerous native fish populations dependent upon the river for habitat and sustenance.
What are ecosystem services?
Ecosystem services are the numerous direct and indirect benefits received by humans from their natural environment (e.g. direct material benefits and indirect supporting/regulating benefits influencing nutrient cycling, water quality and climate patterns). However, when promoting conservation, it is important to avoid reductive ‘nature for people’ framing.
What is ecosystem resilience?
Resilience refers to the capacity of a system to resist and recover from perturbation. Biodiversity underpins the resilience of human infrastructure and economic systems, which is now threatened by anthropogenic climate change and extractive industrial practices.
How can we improve ecosystem resilience?
We can improve resilience by improving connectivity, allowing for migration and range shifts as an adaptive response to climate change. We can also help to maintain biodiversity - as species richness, functional redundancy and species abundance all safeguard evolutionary potential and increase resilience. Ecosystems are threatened when they have low resistance to perturbation and low recovery rates associated with perturbation. These ecosystems are often fragmented and polluted, with low biodiversity and no functional redundancy - with small shifts resulting in cascading effects across trophic levels.
Are tree plantations equal in ecosystem service value to native forests?
No. Native, naturally-regenerating forests sequester more carbon, exhibit improved water availability, prevent erosion more efficiently and harbour more species than low diversity plantations.
How do we quantify the economic value of ecosystem services?
Pollination has a value of 1.25bn USD per year, whilst Amazonia generates 20 billion tonnes of rain per day, fuelling the Latin American agricultural economy (worth 240bn USD). The value of ecosystem services to the global economy is approximately 125 trillion per year.
