8/5/2011. Lesson Overview. Disturbance/Fragmentation. Shifting Mosaic. Number one cause of biodiversity loss. Types of disturbance. - Scale, frequency

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Opal French
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Lesson Overview Disturbances Fragmentation

Example 1 Shifting Mosaic Landscape a shifting

- Made up of patches in different phases of

1 Lesson Overview Disturbances Fragmentation Types Measuring Corridors Effects Texas Example 1 Shifting Mosaic Landscape a shifting mosaic. - Made up of patches in different phases of successional development. - Each patch continually changing. 2 Disturbance/Fragmentation Number one cause of biodiversity loss. Types of disturbance - Scale, frequency - Classification 3 1

Disturbance Disrupts community structure and function. - Contributes to patches on landscape. - Can reduce or foster species diversity. 4 Disturbance Characterized by regime or pattern of disturbance.

2 Disturbance Disrupts community structure and function. - Contributes to patches on landscape. - Can reduce or foster species diversity. 4 Disturbance Characterized by regime or pattern of disturbance. - Intensity Total biomass (proportion of species) killed or eliminated. - Frequency Mean number of disturbances within a time interval. - Scale Spatial extent of impact of disturbance relative to landscape size. 5 Degree of Disturbance 6 2

Types of fragmentation Making holes in habitat Sub-dividing with =

of existing patches 7 Measuring Fragmentation Area Connectivity

3 Types of fragmentation Making holes in habitat Sub-dividing with = width lines Breaking into smaller parts Decrease size of patches Loss of existing patches 7 Measuring Fragmentation Area Connectivity Control of dynamics 8 Corridors Connect patches of similar habitat. - Many are man-made. - Hedgerows, lines of trees, streams, highway medians, drainage ditches. Enhance ability of organisms to move among patches. 9 3

Corridor Connectivity Extent to which a species or population can move among patches within the

10 Corridor Filter Effect Corridors may act as filter providing dispersal routes for some

Encourage spread of invasive or exotic species. 11 Road Corridors Dispersal routes for humans.

4 Corridor Connectivity Extent to which a species or population can move among patches within the matrix. Encourage gene flow between subpopulations. 10 Corridor Filter Effect Corridors may act as filter providing dispersal routes for some species but not all. May also spread disease between patches. Encourage spread of invasive or exotic species. 11 Road Corridors Dispersal routes for humans. Dissect landscape. Major source of mortality for wildlife from large mammals to tiny insects. Allow human access to remote areas which lead to negative ecological effects of habitat. 12 4

Spatial Fragmentation Effects Increase - Patch density, inter-patch distance, boundary length, stepping stones and corridors Decrease - Patch size, connectivity, interior-to-edge ratios, core size,

5 Spatial Fragmentation Effects Increase - Patch density, inter-patch distance, boundary length, stepping stones and corridors Decrease - Patch size, connectivity, interior-to-edge ratios, core size, total interior area Patch shape and dimensions may also change. 13 Species Effects of Fragmentation Increase - Isolation, generalists, multi-habitat species, exotics, nest predation. Decrease - Dispersal of interior/specialists, large home range species, richness of interior species. 14 Other Fragmentation Effects Increase in metapopulation dynamics Decrease intra-patch t or inter-patch t heterogeneity Altered disturbance cycles, wind movement, hydrologic flows, nutrient cycling, productivity and gene flow 15 5

- Since 1970, 1,000 new farms and ranches per year are established.

6 Fragmentation Example Private farms, ranches and forestlands account for 84% of the Texas land base! 16 Land Trends in Texas Trend where land divided into smaller parcels. - Since 1970, 1,000 new farms and ranches per year are established. Red indicates areas of high land conversion from agriculture to other land uses. 17 Loss of Agricultural Lands Agricultural land use declined by almost 3 million acres. - 33,000 more farms and ranches on 3 million fewer acres! 18 6

Rates of Fragmentation Top 10 percent of Texas counties experiencing rural land fragmentation. Eastern part of state and outskirts of any major city. Brown indicates increasing rates of fragmentation.

7 Rates of Fragmentation Top 10 percent of Texas counties experiencing rural land fragmentation. Eastern part of state and outskirts of any major city. Brown indicates increasing rates of fragmentation. *USDA Census of Agriculture 19 Implications Farms/ranches too small for traditional farming, ranching or forestry. - Wildlife habitat degradation difficult to manage. Trends suggest improved pasture. - Non-native, exotic grasses increases. - Grassland-dependant wildlife species decline to increase. Limited prescribed fire = brush encroachment. Fragmentation makes land management and conservation difficult. 20 End of Lesson Disturbances Fragmentation Types Measuring Corridors Effects Texas Example 21 7

Habitat Loss and Fragmentation

Habitat Loss and Fragmentation Fuente: Center for Biodiversity and Conservation What is: Habitat Fragmentation? The end result of human settlement and resource extraction in a landscape is a patchwork