What is macroecology?

• First popularized in 1989
• But studies using these sorts of methods have been around since the 1800s
• No true definition of what it is:

The search for major, statistical patterns in the types, distributions, abundances and richnss of species from local to global scales

(Lawton 1999). This is very broad. Some specifics:

Macroecology specifics:

• Species-area relationships
• Latitudinal diversity gradients
• Range size distributions
• Abundance distributions
• Altitudinal/elevation patterns (how communities change as climbing mountains)
  • Chapt. 2.7 of "Patterns and Process in Macroecology" book

Species-area relationships

• The slope of species richness per area surveyed has remained the same in a study in Sweden over 100 years (1921 - 2021)
• Historically, this was often studied using literal islands, but has also been studied in habitat patches (Island Biogeography)
  • (Population Genetics - Migration#Example Water Snakes in Lake Erie)
• In math terms: Species richness is $c\times Are{a}^z$ or $\log S=z\log (\text{Area})+\log c$ (Linear models)
• The slope $z$ of this species area relationship is surprisingly consistent around the world, between 0.2 and 0.4
• Counting the number of birds within a small to large area within the UK - linear slope between log area and log species
  !1_Macroecology_NoActivity, p.39

Implications

• Since bigger areas have more species, this has influenced conservation decisions: the bigger area protects more species (complicated topic) (Applied Ecology)
• Can be used to preict the impact of habitat loss on species richness (instantaneous) - though this doesn't account for long-term "extinction debt"

Latitudinal Diversity Gradients

• Generally there are more species near the equator and less near the poles
• There are exceptions and variations

Dimensions

• Macroeceolgy are studies that are large in one dimension or more - large in space, time or taxonomy (breadth)...
  • Macroevolution (week 3) we will study large-scale diversity of mammals
  • A large phylogenetic study proved that mammals had already been diversifying before the dinosaurs went extinct (Bininda-Emonds 2008)
• A macroecology study can examine variation in one species over a large area
• "large" is defined relative to the species of course
• Increasing computing power has let us examine much higher resolution

Conservation

• The idea of "biodiversity hotspots" has come from macroecology - related to endemism
  • These are areas that have at least 1500 of the world's 300,000 plant species as endemics.
  • This tends to correlate well with other taxa
    !1_Macroecology_NoActivity, p.63
• Studies have also used macroecology to assess how protected areas work to conserve biodiversity - Gray 2016 proved that species richnss is higher in protected areas than outside, around the globe
• IPBES is he international org to synthesize scientific literature for policy recommendations for global assessments of biodiversity

Methods

• Generally - "big data" is important, broad definition
• Older studies simply combined range maps, but statistical analyses (linear models) is important for taxa where we don't have as much detailed data as we do for e.g. birds
• Meta-analysis
• Often we use remotely sensed data (NDVI, biomass, carbon density), and datasets like GBIF
• "globally distributed experiments" - people around the world preform the same methods to contribute to a study
  • Helsinki "LifePlan" is a global biodiversity experiment