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Transcript
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) 26 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.