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Introduction to Landscape ecology and matrix Dr Elias Bizuru Senior lecturer National University of Rwanda Phone: +250 78 857 60 52 Email: [email protected] ebisous@yahoo fr [email protected] Past landscape Carboniferous period… Ecologie de la conservation 2 Jurassic landscape…. Ecologie de la conservation 3 Cretaceous landscape…. Ecologie de la conservation 4 Eocene epoch: This is a wetland inhabited by bats, birds, and primitive frogs. In this day and age, the top predators d are giant i ground d birds bi d such h as the h Diatrima. Poised at this moment in time, evolution almost took a turn toward preventing the development of large mammals due to the dominance of these birds. Ecologie de la conservation 5 A scene from the Oligocene, 30 million years in the past. Here a Paleomastodon and proto-hippos enjoy a wallow at the river's edge, unconcerned that their distant descendants will one day spread across most of the continents and brave the harsh conditions of the Ice Ag e Ecologie de la conservation 6 Miocene epoch p in north America… Ecologie de la conservation 7 Pliocene epoch…. Ecologie de la conservation 8 Pleistonece period: Australopithecus appeared… Ecologie de la conservation 9 Plant history…. Ecologie de la conservation 10 What is landscape ecology? • Landscape ecology is the study of structure, structure function, and change in a heterogenous land area composed of interacting ecosystems. ecosystems • IIt is i an interdisciplinary i di i li science i d li with dealing ih the interrelationship between human society and d our living li i space. Principles of Landscape Ecology • To understand landscape ecology, we have to focus on some of its important principles: landscape composition, structure, function, and change. – Composition p involves the ggenetic makeup p of populations, identity and abundance of species in the ecosystem, and the different types of communities present. – Structure involves the variety of habitat patches or ecosystems t and d their th i patterns—the tt th size i and d arrangement of patches, stands, or ecosystems— including the sequence of pools in a stream, stream vertical layering of vegetation. – Function involves climatic, geological, hydrological, y g , ecological, g , and evolutionaryy processes such as seed dispersion or gene flow. – Change involves the continual state of flux present in ecosystems. 14 • A landscape consists of three main components: a matrix, patches, and corridors. • If we understand these components and their interrelationships, we can make better management decisions at the landscape level. Landscape structure LLandscapes d consist i t off the th matrix t i (the (th dominant d i t feature), patches, and corridors that connect the patches. t h • The matrix, matrix the dominant component in the landscape, is the most extensive and connected landscape type, type and it plays the dominant role in landscape functioning. • If we try to manage a habitat without considering the matrix, we will likely fail to provide what wildlife need in that area. • The characteristics of matrix structure are the density of the patches (porosity), boundary shape, networks, and heterogeneity. • If an area has been broken up but the patches are fairly f i l close l t th the together, th patches t h are still till dense enough to be useful for animal movement. t However, if you open up a large forested area by creating small openings, the patches may not be dense enough to sustain certain kinds of animals Patches • Patches are nonlinear surface areas that differ in vegetation and landscape from their surroundings. • They are units of land or habitat that are heterogeneous when compared to the whole. • Theyy include four different types: yp disturbance,, remnant, environmental resource, and introduced • Disturbance patches are either natural or artificial. They result from various activities, activities including agriculture, forestry, urbanization, and weather. If left alone, a disturbance patch will eventually change until it combines with the matrix. • R Remnant patches h result l when h h humans alter l the h landscape in an area and then leave parcels of the old patches are ggenerallyy more habitat behind. Remnant p ecologically stable and persist longer than disturbance patches. • Environmental resource patches occur because of an environmental condition. • Introduced patches are ones in which people have brought in nonnative plants or animals or rearranged native species. species Animals A i l moving i from f one area to another h can also bring in these nonnative elements. 24 Ecosystem Loss and Fragmentation Frey © AMNH‐CBC What is Fragmentation? The end result of human settlement and d resource extraction in a landscape is a patchwork of small, isolated natural areas in a sea of developed land… Langham © AMNH‐CBC Gascon et al. 1999 Fragmentation g can also be thought g off as “a disruption of continuity” Source: Sterling © AMNH‐C 28 Fragmentation and Spatial Scale: Scale is I Important t t Fragmentation ag e a o can ca occur occu aat d differing e g sca scales es and a d has as different impacts at each level Region Watershed Site or Local Fragmentation at regional scale Fragmentation at ecosystem level Nyungwe Fragment Mabayi Fragment Rwegura Fragment principal Fragment Bugarama‐Teza Main underlying Causes of Fragmentation • Agriculture • Urban p development • Logging • Mining • Roads • Hydroelectric dams • Groundwater G d extraction Source: Bureau of Land Management/ photo by Robyn Hertz Loss and Fragmentation Impacts • Most of the earth’s biomes have experienced habitat loss • Extent and rate of loss are hard to quantify! – – – – Limited data in some regions Differences in classification methods Lack of historical data Erratic or poor government reporting Major Biomes and Their Vegetation • Tundra – no trees, lichens, grasses and shrubs • Taiga (or Boreal Forest) – coniferous evergreens • Temperate forests – include evergreens (spruce), deciduous forests (oaks) (oaks), mixed forests forests, and temperate rain forests (sequoias) • Tropical T i l rain i forests f t – greatest t t amountt off di diversity it in vegetation (vines, orchids, palms) • Grasslands – grasses, prairie clover • Deserts – cacti, small bushes P R E S E N T D A Y B I O M E S tundra taiga taiga desert temp. decd. forest desert grassland trop. rain forest scrub forest temp rain forest desert Major Terrestrial Biomes • • Geographic distribution of biomes are dependent on temperature, precipitation, altitude and latitude Weather patterns dictate the type of plants that will dominate an ecosystem faculty.southwest.tn.edu/. ../ES%20%20we16.jpg Natural Fragmentation & Habitat Heterogeneity Source: Ansel Adams for the US Department of the Interior 1933‐ 1942 Reasons of high diversity in the ggraet lakes region g Distribution of rainforests 18.000 BC Distribution of rainforests 6000 BC Phytodiversit y off Africa f Human caused fragmentation vs. natural patchiness Patch Characteristic Structure Wildlife habitat Contrast between patches Edge effects Roads & other Human structures Human Natural Complex Suitable to many species Simple Not always suitable & to fewer species Less Less intense Uniquely occur and create unique dangers High Higher intensity Never Th Process The P off Fragmentation F t ti Example of the Forest Fragmentation Process 1975 Moist Forest, Rondonia Brazil Source: USGS EROS Data Center Example of the Forest Fragmentation Process 1986 Moist Forest, Rondonia Brazil Source:USGS EROS Data Center T h i l TTerms ffor FFragmentation Technical t ti P Process Perforation ‐ Holes punched in a landscape Dissection ‐ Initial subdivision of a continuous landscape Fragmentation ‐ Breaking up into smaller parts Shrinkage ‐ Reduction in size of patches Attrition ‐ Loss off patches h Source: Murphy©AMNH‐CBC Biological Dimensions of the Fragmentation Process All Images: © AMNH‐CBC “Area‐Sensitive” Area Sensitive species Neotropical migrant songbirds P r o b a b ility o f O c c u r a n c e Scarlet Tanager 1 0,8 0,6 0,4 0,2 0 0,3 1 3,2 10 32 100 320 1000 3000 ( ) Area of forest (ha) Modified from: Robbins et al. 1989 50 Why Larger Patches usually support more Species? • More heterogeneity in larger patches • Large fragments support larger populations • Smaller fragments g support pp smaller populations p p • A smaller p population p increases the likelihood of local extinctions Long‐term effects of reduced patch area on extinction rates Modified from: Newmark 1996 How Fragmentation reduces Metapopulation viability i bilit • Reduces patch and population thereby increasing extinction rates sizes, • IIncreases inter‐patch i t t h distance, di t reduces d migration rates between patches, reducing th the lik lih d off local likelihood l l populations l ti sustaining one another Source and sink populations • Metapopulations often have a complicated structure • Some populations often have higher growth rates and provide migrants that sustain other populations = sources • Others cannot sustain themselves and depend on migrants from elsewhere = sinks • Be cautious: sometimes the smallest populations actually have the highest reproductive success and actually sustain the metapopulation. Depiction of a metapopulation Metapopulations and Dispersal Source: Gibbs Edge Effects • Physical – Microclimate changes in light temperature, light, temperature & wind – Humidity ≅ 100m • Biological – Exotic Plants and Insects – Invasive Plants, Insects and animals – Bird Density ≅ 100m • Synergistic – Fire – Hunting pressure by humans and other predators Frey©AMNH‐CBC Edge Effects in Conservation Reserves Area: 16 sq K Edge: 16 K Reserve A Area: 16 sq K Edge: 20 K Reserve B Area: 16 sq K Edge: 32 K Reserve C Management of Fragmented Landscapes: Maintaining Biodiversity • • • • • • Which species are most vulnerable? Conduct a landscape analysis ‐ where are the big blocks and d connections? i ? Evaluate the landscape in a regional context Can planning avoid further fragmentation fragmentation, ee.g., g retain corridors that increase connectivity of patches? Minimize edge effects Remember small fragments Characteristics of Species Vulnerable to Fragmentation • Species with specialized habitat needs p with limited dispersal p abilities • Species • Species with low fecundity • Species vulnerable to hunting • Species that are arboreal • Co‐evolved species • Ground nesters vulnerable to predators Identifying Core Regions at the Regional Scale Source: Ersts ©AMNH‐CBC Evaluating fragment isolation and scoping out potential corridors Source: CERU, University of Pretoria Evaluatingg Connectivityy at the Regional g Scale: The Proposed Limpopo Source: CERU, University of Pretoria Evaluating Riparian Zones as Corridors at the Local Scale Frey © AMNH-CBC Example: The Effect of Implementing a Prohibition on Riparian Zone Clearing Source: Courtesy of the USDA Natural Resources Conservation Service Conclusions • FFragmentation i i a complex is l process and d similarly i il l evaluating the impacts of fragmentation on different landscapes and species is complex • Key issues are the total area, isolation and composition of patches that remain in a landscape following fragmentation • Fragmentation is an issue at many scales from local to regional, g with different impacts p at each scale • Simple land use guidelines can have direct and major effects on the level of fragmentation in a landscape