In the cloistered tradition of scientific specialization, most ecologists think of the world narrowly, as a system of natural environments beleaguered by human activity. They live, as Aldo Leopold put it, in a world of wounds. They have reason to think this way. Today, less than 10% of the land surface remains in a mostly unchanged state, and only 4% has been set aside in natural reserves. In their own specialty, planners and landscape designers tend to stay in their larger and wholly different world. For them, the bulk of the land has been given over to humanity; and now, they say, people must redesign it to their liking.

Neither view, taken to exclusion of the other, is viable any longer. Ecologists increasingly recognize that they must extend their science to embrace artifactual environments. More reflective planners and landscape designers understand that they cannot afford to ignore organisms - the right organisms - needed to sustain a healthy, pleasing environment. A few scholars, of which Richard Forman is a notable example, have come to focus on the intellectually rich domain of overlap between the two fields. The result of their deliberate intermediacy is the new discipline of landscape ecology.

In Land Mosaics, Forman joyously embraces the human-altered environment and proposes that its living part can be improved by use of the best principles of environmental biology. He recognizes, as the book's title implies, that the real world consists of finely fragmented habitats. The pieces range from radically altered urban parks and gardens to remnant pockets of the original environment. Across periods as short as a few years, living species arrive, impinge, dominate, yield, and disappear in this kaleidoscope. The vast majority of the inhabitants we never see, because they are too small and obscure: creepy-crawlies, immense in diversity, from insects to fungi and bacteria. All together, they are as important as the towering trees and the birds on which our attention is ordinarily focused. The species that can survive in the habitat fragments come together to determine the health and beauty of the places in which we live.

Forman and other scientifically educated landscape ecologists address the question: ‘Given that humanity is now in charge of most of the land surface, and responsible for it, what designs of the terrestrial landscape are best for the rest of life, and therefore for us?'

Artists and photographers use contrast to create stunning images. High contrast is attained by accentuating the difference between adjacent areas, and by sharpening the boundary. This chapter focuses on the myriad types of boundaries that separate ecosystems or land uses in a landscape (Fig. 3.1).

Of what use are these boundaries within a landscape? In wildlife management edges typically have an abundance of game and other animals that move along or across boundaries. In questions of biodiversity and land fragmentation, the ratio of edge to interior habitat is critical. In aesthetics, views are often dominated by edges. In forestry, edges are commonly characterized by crooked trunks and blowdowns. In agriculture, edges are often the source of pests, as well as predators controlling pests. In soil erosion control, boundaries cause wind speed changes and turbulence. In park and nature reserve management, boundaries may be barriers to human overuse. In detecting global climatic change, boundaries are often proposed as a sensitive indicator, the ‘canary in the mine'. And in sustainability issues, humans are edge species, but by carving up the land and increasing edges enormously, we eliminate the key values of large patches, thus degrading our landscapes.

Useful literature reviews are available for boundary ecology as a whole (Holland et al. 1991, Hansen & di Castri 1992), as well as for ecotones360,1769,403 and the edge effect as related to biodiversity and wildlife.1700,684,1941 Boundaries between land and water are analyzed in chapter 7.

The present chapter begins with the structure of boundaries, and the developmental mechanisms controlling them. Next, functions are presented, including the edge effect and movements and flows across boundaries. Width and curvilinearity are examined as major variables affecting both anatomy and flows. Finally we explore boundaries moving on the land.

TYPES AND ABRUPTNESS

Boundary types and theory

In chapter 1 we noted that introducing energy causes a system, such as a landscape, to become spatially heterogeneous in one of two ways.503

Nature creates corridors in the form of streams, ridges, and animal trails. Humans create roads, powerlines, ditches, and walking trails. How do the two types differ? Nature's are curvy, until humans straighten them. Nature's are continuous until humans superimpose grids on them, and create gaps. Human corridors are generally narrow and costly to maintain.

Corridors, as strips that differ from their surroundings, permeate the land. Vegetation corridors contribute significantly to many goals of society, here lumped into six categories.491 First, corridors provide biodiversity protection, including key riparian habitats, rare and endangered species, wide-ranging species, and dispersal routes for recolonization following local extinction. Second, corridors enhance water resource management, such as flood control, control of sedimentation, reservoir capacity, clean water, sustainable fish populations, and fishing. Third, linear strips may enhance agroforestry production by acting as windbreaks for crops and livestock, controlling soil erosion, providing wood products, and preventing desertification. Fourth, recreation in corridors includes game management, wildlife conservation for nature enjoyment, and hiking, bicycling, boating, and skiing in suburban greenbelts. Fifth, community and cultural cohesion may be enhanced with greenbelts, which create neighborhood identity, provide wildlife corridors crossing roads that concurrently inhibit strip (ribbon) development along a road, and function as regional topographic barriers that enhance cultural diversity. Sixth, corridors provide dispersal routes for species

isolated in nature reserves, and coastal strips threatened by rising sea level in the event of climatic change.

Useful reviews of corridor attributes are given by Forman & Godron

(1986), Schreiber (1988), Brandie et al (1988), Bennett (1990a, 1991),

Saunders & Hobbs (1991), Forman (1991), Malanson (1993), and

Smith & Hellmund (1993). Reviews of specific topics include the corridor

as a conduit685,688,1228, the corridor as a filter174,1038,130, road and roadside

vegetation109,111,1492, and trails.968,1842

Windbreaks, hedgerows, and wooded strips are presented in chapter 6, and stream and river corridors in chapter 7. Corridors are also commonly interconnected to form networks, as explored in chapter 8.

This chapter begins with general patterns and principles that apply to virtually all corridors.

Dreams of Utopia have sparked the establishment of communities in every century. Social, political, or religious fervor and commitment have created such communities, especially in rural landscapes. Yet rather few of these experiments have lasted a century. At the other extreme are civilizations and societies that have continued for centuries and even millennia (Fig. 14.1). In all cases success or failure depends both on human dimensions and the land.

Two central components of sustainability are thus introduced. The time frame is over human generations, and the key characteristic is a dynamic with equal emphasis on human and environmental dimensions. The preceding chapter on land planning and management elucidated principles based on this combination of land processes and human resource use. But the time scale was years (or up to a few decades), the normal framework for planning, design, conservation, management, and policy. The difference in time scale is the primary characteristic separating sustainability from normal year-to-year planning. For planning over human generations, if we are to learn from history, the most instructive history is of human-land interactions over two or more centuries.286

Most sustainability literature focuses on the globe.1414,286,1929,768 Only a few countries have begun seriously addressing the implications of sustainability.434,1002,1431,476,778 Although this chapter touches on the built environment, the idea of sustainable urban development is not directly addressed. However, agriculture, economics, forestry, fisheries, sociology, and more recently ecology have taken a particular interest in sustainability, often considering it within their own disciplines. Surprisingly, the role of spatial arrangement of land is commonly overlooked.. Little literature on sustainability exists at the landscape and regional scales.492 Yet these scales may be the most important for attaining sustainability.

This chapter assumes general familiarity with principles in most preceding

chapters; indeed many points will otherwise be unclear or counterintuitive.

The chapter begins with the basic concepts of sustainability.

It then focuses in detail on key sustainability attributes, organized by

time, space, humans, assays, and adaptability. Next, we learn from

human histories, and briefly revisit regional ecology.

Five minutes after leaving a tropical city one of the plane's two engines dies. The plane begins dropping. Rich primeval rainforest awaits on one side, and town-dotted farmland on the other. Someone snaps an instant photograph, carries it to the open cockpit, and the pilot explodes in laughter. The passengers remain petrified until we slip over a ridge and bounce onto an unlighted runway.

The object spread out beneath an airplane window, or on an aerial photograph, is the subject of this book. Indeed, an aerial vantage provides a goldmine of information on the ecology of large land areas, such as landscapes and regions. For example in Fig. 1.1, one can predict with some confidence that the forest has many more interior species than the wooded patches on the right. Animal movement funnels through the lobes or peninsulas of the forest. Wind erosion is high in the corridor gaps on the left. Cool-water fish are probably missing from the stream in the far right. The clearing at the top has been expanding, while the clearing below it is contracting. The ecologically optimum location for a cluster of houses is by the field-forest edge in the upper right. The evidence for interpretations such as these and many more is presented in this book. Of course, dropping from the sky to examine the land closely is also essential.

MOSAICS AND THE PATCH-CORRIDOR-MATRIXMODEL

From an airplane, land almost always appears as a mosaic. The glorious mosaics of St. Mark's in Venice or the University of Mexico appear as a pattern of colored patches and strips, usually with a background matrix. Tiny stones of different colors are aggregated to create the patches, strips, and matrix. The land appears much the same. Individual trees, rocks, houses, and so forth are the tiny stones. Woods, fields, and housing tracts are conspicuous patches. Roads, hedgerows, rivers, and powerlines are equally striking corridors. Grassland, forest, rice culture, or another land use often forms a background matrix. In short, the individual trees, shrubs, rice plants, and small buildings, analogous to the tiny stones in the artist's mosaic, are aggregated to form the pattern of patches, corridors, and matrix on land.

'Think globally, act locally’ is a phrase much in vogue. Yet it has two problems. First, few people will ever give primacy to the globe in decision-making. Second, local considerations overwhelmingly determine actions. Indeed, these are two roots of environmental and societal problems etched widely in the land. Typically, our best soils are thinned by erosion or covered by suburbs; biodiversity and wildlife in large wooded areas are impoverished by dispersed logging; critical riparian and hedgerow corridors are cut or razed by macroagriculture; productive land is desertified by irrigation and overuse; and parks are surrounded by the tightening noose of development.

Can this unraveling of the land, as the primary capital of a nation, be reversed? Land patterns seem logical and ecological in exceptional places within, for example, Britain, Romania, Costa Rica, Australia, and the USA, as well as in certain spatial models. In these cases efforts in design, planning, conservation, and decision-making seem both visionary and practical. They are directed at agricultural landscapes, suburban landscapes, forested landscapes, or regions. At these scales the environment, economics, and society coalesce. The landscape and region are the central linkage between global and local.

The philosophic framework for this chapter therefore might be that we better ‘Think globally, plan regionally, and then act locally .

The perennial challenges in planning, design, and management of an area are not only to take a broad spatial view and a long temporal view, but also to address all major environmental and human issues present. Water, transportation, biodiversity, aesthetics, sense of community, food production, and much more are the essential factors.

The landscape mosaic was presented as a whole in chapter 1. Now we begin dissecting it into its building blocks, beginning with patches. A patch is a wide relatively homogeneous area that differs from its surroundings (see glossary in chapter 1 appendix). Patches have familiar attributes, such as large or small, rounded or elongated, and straight or convoluted boundaries. These attributes in turn have widespread ecological implications for productivity, biodiversity, soil, and water.

Why are these patch characteristics so important? In forestry the size of woods affects road construction and erosion, how many trees are wasted in edge effects, and the success of tree reproduction. In suburbanization planning the size of housing developments and nature reserves are common controversial issues. In aquifer and lake protection water quality depends on a large patch of natural vegetation. In managing stream systems for fish and fishermen, the size and number of natural patches is critical. In nature reserve design, is it better to have one large patch or several small patches? How many large patches are required to maintain the biodiversity of a landscape? In managing game, small patches are frequently created. And in agriculture an optimum field size has both ecologie and economic implications.

Several of the topics included are reviewed by Forman & Godron (1986). Other useful reviews include: patch dynamics1320; the traditional species-area concept; island biogeographic theory1023,1323,302,564,1901,198,1763,1536; remnant patches in landscapes683,1490,1536; and genetics in patches1595.

This chapter begins with the origins and half-life of dynamic patches. Patch size effects are examined for ecosystem processes. Species-area curves and island biogeographic theory lead to evaluating species numbers in remnant and disturbance patches in a terrestrial mosaic. The roles of genetics and minimum viable populations are introduced. Finally we evaluate the importance of number of large patches present.

PATCH DYNAMICS: ORIGIN AND PERSISTENCE

The fortuneteller who predicts change is always right. We may dream of constancy or stability, but change, the universal law, is a key to understanding. Indeed, because change always extends over a limited area, it causes or affects a patch.

A sandbox is an ideal place. Children are protected from the outside, and become engrossed in creating their own micro-landscapes. They draw networks that crisscross and squiggle. They smooth the surface with their hands forming a surrounding matrix. And together they create a mosaic for the whole sandbox. The mosaic is continually changed and molded, and usually punctuated by big disturbances.

Everyone should have a sandbox, even a tiny one for fingers. The soothing effect, the manifest creativity, and the modeling for landscape and regional ecology are rich benefits. Metaphorically we are the children and the world is our sandbox. To get along and still have a nice sandbox, we need to find land designs that make sustainable sense. Networks and the matrix, analogous to those molded by the children, are the subject at hand.

This chapter moves to a new level. Preceding chapters have explored the attributes of patches and corridors, the building blocks of landscapes. Movements and flows to and from adjacent land have been included as patch-matrix or corridor-matrix interactions. Now we explore the matrix, and hook building blocks together to form mosaics. Patches, corridors, and matrix are combined in distinctive ways to create the finite number of common mosaics on land.

The primary importance of this subject is planning. One may sculpt an individual patch or corridor to attain desired objectives. But sculpting a matrix or network of several spatial elements on a farm, park, forest, refuge, or town requires planning by the owner or manager. And creating a logical mosaic for a whole landscape or region requires regional and government planning.

Perhaps the only overview of the subject is by Forman & Godron (1986). However, useful reviews of portions include: transportation networks1670,995,646,1518; hedgerow networks1337,948,1114,1116; windbreaks174; and the matrix.501

The chapter begins with the development of networks, and how to measure them. Dendritic and rectilinear networks are contrasted, and the functioning of networks is explored. Next the structure of a matrix is presented. And we conclude with matrix dynamics.

Vertebrates are often marked and followed to determine their habitat requirements, and the locations of their encounters with other animals. Suppose we try this on a suburban family using radiotracking techniques. Miniature radio transmitters are worn as fancy belt buckles or earrings, and you have a high-tech antenna to locate family members at any time. You record the cluster of workplaces, food stores, roads, schools, local parks, night spots, and so forth visited. Each person's 'home range’ is then mapped using the spatial arrangement of locations and routes taken. The amazingly different mosaics would help planners design better suburbs, based on the cluster of locations that people use, and perhaps need (S. B. Warner, Jr., pers. commun.).

In previous chapters we considered patches, corridors, and matrix by themselves. Now we begin hooking these building blocks together to form mosaics. Mosaics are evident at all scales. Here, we focus on the neighborhood clusters of ecosystems or land uses, plus whole landscape and regional mosaics. On land there may be a limited number of common mosaics to understand.

In landscapes and regions context is usually more important than content. That is, the surrounding mosaic has a greater effect on patch functioning and change than do the present characteristics within the patch. Context here includes three components: adjacency, neighborhood, and location within a landscape. ‘Adjacencies are the spatial elements in contact with the patch or site of interest (chapter 2). ‘Neighborhood’ is the encompassing local mosaic linked by active interactions. Neighborhoods and locations within a landscape will be the emphasis here in understanding context.

The name of the book

Reading Medieval Latin is designed to follow on from Reading Latin (P. V. Jones and K. C. Sidwell, Cambridge University Press, 1986). But it can be used by any student who has learned the basic morphology and syntax of Classical Latin taught in Reading Latin sections 1–5.

How the book is arranged

The book is in four parts, each part being divided into five sections. Part one presents texts to illustrate the culture in which Medieval Latin (ML) developed and the sources on which its writers were nurtured. Part two presents selections of Latin written between c.500 and 1000. Parts three and four give fuller treatment of the Latin writing of the eleventh and twelfth centuries. A list of sources can be found on pp. xi–xvi.

Each part, section and text has introductory material, with suggestions for further reading. Each text has a commentary with help on language and content. In most cases, reference to text is by line number. However, reference is sometimes by numbered paragraph (e.g. in section 3). The linguistic help is keyed in to two brief appendices on Orthography and Grammar, which are referred to by O.0 etc. and G.1 etc. respectively. Other grammar references are to Reading Latin: Grammar, Vocabulary and Exercises (RLGVE) or Reading Latin: Reference Grammar (RLRGr), found at RLGVE pp. 448–56.