Taking Nature's Pulse: Section 1: Primer on Biodiversity: Importance and History in B.C.

1. A Primer on Biodiversity: Its Importance and History in British Columbia

1.1 What Is Biodiversity?

In the 1980s, the eminent biologist Edward O. Wilson coined the term 'biodiversity' as a shorthand for biological diversity.^a Biodiversity describes the diversity of all living creatures and their interactions. It is this complex web that sustains life on this planet. From among many possible definitions, Biodiversity BC uses that of the Canadian Biodiversity Strategy: the variety of species and ecosystems on earth and the ecological processes of which they are a part - including ecosystem, species and genetic diversity components. ^6,7

The interaction of species, ecosystems and processes is dynamic and links multiple scales (from centimetres and days to hundreds of kilometres and millennia) that collectively shape biodiversity.⁸ In a forest, for example, interactions across the range of scales include: physiological processes that affect the life cycle of leaves; competition between neighbouring plant species that affects populations; disturbance and predation processes; and climatic processes that influence the physical and biological character of landscapes and regions.

Ecosystems are complex, dynamic and adaptive systems that are rarely at equilibrium. However, the more an ecosystem maintains its integrity, the more resilient it is and the better it can withstand shocks and rebuild itself without changing to a different state. As ecological functions are impaired and systems simplified, resilience is reduced, making such ecosystems more vulnerable to biophysical or human-caused events that they would otherwise tolerate.⁹ Maintaining ecological processes promotes ecological resilience and helps ensure the continued functioning of dynamic, natural ecosystems.¹⁰

^a The first published use of 'biodiversity' was in 1988, in the title of the proceedings of the first U.S. national conference on the subject, edited by Wilson (Biodiversity, National Academy Press, 1988).

1.1.1 genetic, species and ecosystem diversity

Complex concepts such as biodiversity are often easier to grasp if reduced to their component pieces. While this approach does not give a complete picture of how these pieces interact and combine to create biodiversity, it helps us understand different aspects of biodiversity. The various levels of organization within biodiversity (e.g., genes, species and ecosystems) express different features of the complexity and value of biodiversity and interact with each other through ecological processes. Genes make up species, and species (linked by ecological processes) inhabit ecosystems (Figure 2), with smaller ecosystems nested within larger ones. Ecosystems vary enormously in size.¹¹ They may be as tiny as a drop of pond water or a glacial rivulet, or as vast as the Stikine River watershed, the northwest Pacific coast or the whole planet.

Genes

Genes are the working units of heredity; each gene is a segment of the DNA molecule that encodes a single enzyme or structural protein unit. Genetic diversity is the foundation of all biodiversity. Genetic variation permits populations to adapt to changing environments and continue to participate in life's processes. Study of subspecies and populations can reveal how organisms respond to their environment, which may not be evident when looking only at the species level. Genetic diversity is continuously changing from generation to generation as a result of natural selection and random effects such as mutation.

In the long history of life on earth, genetic variants of many species have evolved, and are still evolving, in response to changing local environmental conditions. For example, the current, highly productive runs in the Bristol Bay sockeye salmon (Oncohynchus nerka) fishery in Alaska originated from low-producing runs that responded to mid 1990s climate changes.¹² Figure 3 illustrates how genetic variations influence the fur colour of the American black bear (Ursus americanus), which occurs as different colour morphs (see also Section 2.4.1.2, p. 75).

Species

Species (and their subspecies and populations) are generally considered to be the only self-replicating units of genetic diversity that can function as independent units. In the case of most living organisms, each species generally represents a complete, self-generating, unique ensemble of genetic variation, capable of interbreeding and producing fertile offspring. Some animals¹³ and many plants¹⁴ can also exchange genes through hybridization, which sometimes results in new species (see Section 2.4.1.4, p. 82).

In addition to the millions of species that biologists have already documented worldwide (ranging from microscopic viruses and bacteria to large mammals), many millions more have yet to be identified and categorized. When species become extinct, diversity is lost at both the species and genetic levels and cannot be recovered. Species, like genes, do not exist in isolation. They interact with other organisms in groupings called communities. Retaining all member species helps maintain community resilience.

Ecosystems

An ecosystem is a dynamic complex of plant, animal and microorganism communities and non-living (abiotic) elements, all interacting as a functional unit. An ecosystem's character changes as community members and physical contexts change, sometimes crossing a threshold of tolerance within the system that results in its inability to return to its previous form. For example, severe winter temperatures regulate the survival of mountain pine beetle (Dendroctonus ponderosae) larvae.¹⁵ Without this controlling mechanism, the increase in larval survival over a period of years can result in a major shift in the character of interior pine forest ecosystems. Text box 16 (p. 105) describes the impact of the current mountain pine beetle epidemic on B.C. forest ecosystems.

1.1.2 Composition, Structure And Function

Besides being examined at the various levels of organization, biodiversity can also be described in terms of attributes such as composition, structure and function.

Composition is the identity and variety of an ecological system. Descriptors of composition are typically lists of the species resident in an area or an ecosystem. Measures of composition, such as species richness and diversity of species, can help demonstrate how biodiversity in an area is faring.

Structure is the physical organization or pattern of a system; for example, the size and spacing of trees in a landscape. Measures of structure, which often describe the habitat of species, reveal arrangements and patterns in both living and non-living components of the environment. These necessarily span a wide range of scales and patch sizes to encompass the natural range of life forms and the ways they respond to the environment (Figure 4) and include the mosaic pattern of communities across landscapes.

Function refers to the result of ecological and evolutionary processes. Examples of function include gene flow (resulting from processes such as dispersal and reproduction) and nutrient cycling (resulting from processes such as photosynthesis and decomposition). Measures of a function must be designed specifically for that function, and perhaps for each of its component processes. For some of the most critical functions, including water purification, nutrient cycling and pollination, scientists know only a fraction of the species and processes involved - and not necessarily the most important ones.

These three biodiversity attributes are inseparable. Composition changes as structure changes; functions and processes change as composition changes. Changes in structure can influence processes such as herbivory and predation, and these processes can change species composition. Changes in composition, such as relative abundance of certain species, can alter structure, leading to further changes in composition. For example, when large predators are lost, populations of large browsers and grazers may increase to the point that certain vegetation elements are eradicated, thereby eliminating other species dependent on that vegetation. The loss of wolves (Canis spp.) and cougars (Puma concolor) in the eastern United States and the subsequent increase in deer (Odocoileus spp.) populations have locally eliminated many ground- and shrub-nesting birds and could lead to the demise of local hardwoods (e.g., oak [Quercus spp.] and American beech [Fagus grandifolia]).^16,17,18 On Haida Gwaii/Queen Charlotte Islands, where cougars and wolves do not naturally occur, high numbers of introduced Sitka black-tailed deer (Odocoileus hemionus sitkensis) have had a severe impact on western redcedar (Thuja plicata), have browsed Sitka spruce seedlings (Picea sitchensis) to the point that moss sometimes grows faster than the seedlings and have kept at least one plant species, western oxypolis (Oxypolis occidentalis), from flowering.¹⁹

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1.2 Why Is Biodiversity Important?

Biodiversity provides a long list of services critical to supporting life on earth (Figure 5).²⁰ Such ecosystem services directly and indirectly contribute economic value. Ten years ago, the global economic value of 17 ecosystem services for 16 biomes was estimated to be in the range of $US16-54 trillion per year, with an average value of US$33 trillion per year.^a,21

Biodiversity also provides diverse cultural services, such as opportunities for spiritual and religious experiences, education, recreation and an aesthetic connection with nature that is exemplified in many art forms.^22,23 These cultural values have remained important even with increasing urbanization and are perhaps most obvious among Aboriginal peoples whose connections to nature are well maintained. For example, western redcedar and yellow-cedar (Chamaecyparis nootkatensis) are culturally important to coastal First Nations (see Text box 2, p. 13).²⁴ Both species are also under increasing threat due to climate change.^25,26

Many people believe that humans have a moral obligation to protect all life forms for their own sake, as well as for their value to future generations. A world without the services provided by species and ecosystems is unimaginable. For example, if major groups of decomposer organisms were to fail, organic debris would simply accumulate, and nutrient cycling, plant growth and food production would come to a halt. Pollination of food plants by insects accounts for about one of every three mouthfuls of food eaten by humans.²⁷ While some species could disappear with little measurable impact, many of the species responsible for the critical ecosystem services required for life and human well-being are unknown. Conserving biodiversity maintains options for future generations.

^a To put this in context, the global gross national product was around US$18 trillion per year.

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1.3 Importance of Biodiversity for First Peoples of British Columbia

First Nations in B.C. have relied on, and helped to sustain, biodiversity in their home territories for at least 10,000 years. More than 30 linguistically distinct indigenous groups have resided here, often in dense populations, especially along the coast and the major river systems. Many of these peoples still live in communities within their traditional territories. Although they have distinctive languages (Figure 6) and cultural traits, they also share many similarities in their cultural practices.

1.3.1 traditional uses of biodiversity

Biodiversity is important to traditional First Nations food systems, technology and medicine (Text box 2). Diets based on a combination of animal and plant foods (including salmon, other finfish, shellfish, marine and land mammals, game birds, birds' eggs, berries and other fruits, green and root vegetables, mushrooms and the inner bark of trees) have nourished and sustained people for countless generations.^30,31,32,33 Plants and animals have also provided a wide range of important material resources: wood for fuel, construction, canoes and implements; sheets of bark and fibrous materials for canoes, cordage, mats, basketry and clothing; pitch for waterproofing and glue; kelp for fishing line and containers; shells, bone and antler for knives, chisels and points; and a host of other substances for dyes, stains, waterproofing, cleansing and protective scents.³⁴ A host of medicines for maintaining health and treating injuries and ailments of many kinds have been derived from plants, as well as some animals and fungi.^{35, 36, 37}

Plants, animals and fungi are also prominent in First Nations' belief systems, art, songs and ceremonies.^38,39 Ceremonial species and those featured in art and narrative are often the same ones that have practical applications.⁴⁰ The richness of Northwest Coast First Peoples' connections with biodiversity is reflected perhaps most famously in their world-renowned art forms, which represent animals, birds, fish and other beings in totem poles, masks, dishes, jewellery, sculptures and paintings.^41,42,43 These designs represent key figures in the histories of families, clans and individuals. Their immense power and compelling form symbolize the depth of human reliance on biodiversity.

Food species alone include at least 100 animal species and 150 plant species across the different nations and regions of the province. Species used for material or technology number at least 100, and medicinal species probably 300 or more. Altogether, about 400 to 500 species (some used for more than one purpose) are named and used or have specific cultural importance for B.C.'s First Peoples. Many others - including many attractive wildflowers that might not be named individually, but are nonetheless recognized and distinguished - have general importance. First Nations' knowledge systems encompass immense expertise about the ecological and morphological characteristics of plants and animals. Many species serve as indicators of traditional seasonal rounds, with the flowering of certain plants, the songs of certain birds or the appearance of certain types of butterflies or other insects marking seasonal changes or signalling the time for important harvest events.⁴⁴

Some plants and animals are so important and well known that First Peoples recognized and named different varieties and strains. For example, the Gitga'at of Hartley Bay have names for at least six different varieties of Pacific crab apple (Malus fusca) and the Nlaka'pmx (Thompson) and Stl'atl'imx (Lillooet) of the southern interior name and use five or more varieties of Saskatoon (Amelanchier alnifolia).^55,56

Biodiversity at the broader scale of community or ecosystem variation is also critically important to First Nations. People routinely moved between ecosystems, from the ocean and valley bottoms to the high mountaintops, to gain access to a range of resources. Generally residing in permanent winter villages on the coast or along rivers and lakeshores, they would, and still do, travel to different sites throughout their territories following the availability of various seasonal resources. They were also able to obtain resources from beyond their own homelands through trade and intermarriage with other groups.^57,58

1.3.2 impacts of biodiversity degradation on first peoples

Erosion of biodiversity in various parts of the province has severely impacted First Peoples and their traditional food systems. Declines and losses of traditional resources, from salmon and abalone to berries and root vegetables, are of great concern. Major changes to traditional food systems have occurred partly as a result of environmental deterioration, and this in turn has resulted in health problems and cultural loss in many communities. First Peoples' lifeways have been directly and consistently impacted by declining populations of game, salmon and other fish, loss of forest cover and loss of access to their traditional land base. It is difficult to assess the extent of their loss in quantitative terms. Only a handful of the 400 to 500 species that were used directly have been assessed as being of provincial conservation concern. Nevertheless, according to the testimony of many elders who have witnessed tremendous change in B.C. landscapes over their lifetimes, most of these species are not as productive or as common as they once were.⁵⁹

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1.4 Biodiversity and Geological History

Geologic history and landscape age play key roles in shaping the biodiversity of a region. In general, old, stable landscapes support more species than young ones because there has been more time for variation to evolve. As well, geologically old regions often have had numerous geographic connections with sources of new life forms from other regions. Landscapes with complex geological histories also tend to have more habitats because the land surface is diverse.

Exceptional events such as glaciation and harsh climates reduce biodiversity and eliminate ecosystems, yet also create isolated pockets of life in which new evolutionary directions are explored.60 British Columbia has experienced widespread glaciation and harsh climates in the past 15,000 years, a short duration in geologic time.^61,62

Global geological processes during the past 100 million years have variously connected and separated B.C. from regions to the east, northwest and south, bringing infusions from a wide range of ecosystems and species and fostering local evolution. For much of the Cenozoic Era (the period of geological history that spans the past 65 million years), the B.C. region was part of a warm, temperate, broadleaf forest biome, which provided the raw materials for modern terrestrial biodiversity⁶³ and extended across the northern hemisphere.

As terrestrial ecosystems developed in the Cenozoic Era, marine biodiversity was largely being shaped by migrations north and south along the Pacific Coast as global temperatures fluctuated. Coastal marine ecosystems developed a north-south pattern of zones. During this period, the oldest fossil member of the salmonid family, Eosalmo driftwoodensis, inhabited lakes and rivers that drained into the Pacific Ocean.⁶⁴ Shoreline ecosystems of 25 million years ago were broadly similar to those of today and many constituent species of that time have modern relatives.

Temperatures declined during the last 10 million years of the Cenozoic, producing the cool and cold climates of the Pleistocene Epoch. During this period of cooling, western North America evolved distinctive temperate and northern floras, faunas and biomes, as well as dry, inter-mountain ecosystems. During this time, the warm, temperate, broadleaf forest biome was slowly replaced by a broad zone of coniferous and deciduous forest.⁶⁵

1.4.1 the pleistocene (ice age) epoch

Beginning 1.8 million years ago, a major Pleistocene Epoch cooling trend initiated northern hemispheric migrations and progressive development of boreal and tundra biomes.⁶⁶ B.C. experienced several widespread glaciations, which reset biodiversity patterns with each advance and retreat.⁶⁷ Taiga (a moist, subarctic forest dominated by conifers, which begins where the tundra ends), tundra and cold, dry steppe ecosystems spread widely across the continent including B.C., alternating in time with coniferous forest ecosystems similar to those of today. A distinctive Pleistocene-adapted, mammal megafauna ranged widely, and cold-adapted species, such as the muskox (Ovibos moschatus), extended into southern B.C. during cold intervals.⁶⁸

1.4.2 before the last glacial maximum: 50,000 to 17,000 years ago

The most important interval for the origin and development of B.C.'s current biodiversity is the past 50,000 years, which includes the last major ice advances. North America, like the rest of the world, was generally cooler, with glacial ice probably covering most of northeastern North America and possibly some B.C. mountain ranges. Vegetation zones were displaced southward and to lower elevations (by 400-500 m). In the northwestern United States, mixed conifer forest alternated in time and space with open ecosystems, dominated by sagebrush (Artemisia spp.) and pines (Pinus spp.) in the interior.⁶⁹

In B.C., extensive subalpine spruce (Picea spp.) and mountain hemlock (Tsuga mertensiana) forests and parkland prevailed between about 48,000 and 30,000 years ago.^70,71 Wetlands seem to have occurred widely and rivers and lakes may have had relatively high sediment loads.

Cold, dry glacial conditions developed across North America, from the north to the mid continent, about 30,000 years ago and intensified to about 20,000 years ago. Steppe ecosystems, including elements of the wide-spread megafauna, such as woolly mammoths (Mammuthus primigenius), seem to have prevailed.^72,73 Current high-elevation alpine species, such as Sitka valerian (Valeriana sitchensis) and American bistort (Polygonum bistortoides),⁷⁴ grew at sea level.⁷⁵ Large glaciers occupied major valleys and fed unstable stream and river systems that transported masses of sediment at their leading edges. A brief respite from these glacial conditions occurred 17,000 to 18,000 years ago when subalpine-like forest returned (at least in southwestern B.C.), before the next intense glaciation began about 15,000 year ago.76 During that short interval, salmonids were found in unglaciated areas such as the Thompson Valley.⁷⁷

1.4.3 The Glacial Maximum: 17,000 To 14,000 Years Ago

The traditional view is that almost all of B.C. was ice-covered during this last glaciation and that B.C.'s terrestrial biodiversity originated with the subsequent migration of species from the south, east and north. From this perspective, B.C.'s biodiversity is a regional variation on evolutionary themes largely developed elsewhere. To a considerable extent this is true. However, recent research, especially DNA studies, suggest that unglaciated zones, or refugia, in B.C. were larger than previously thought and that elements of the province's biodiversity have a long pre-glacial history.⁷⁸

The most widely recognized B.C. refugia are high-elevation sites and some adjacent slopes on Haida Gwaii/ Queen Charlotte Islands and the Brooks Peninsula on Vancouver Island.^79,80 In these areas, alpine and probably high-elevation, cool oceanic ecosystems persisted, resulting in a unique set of plant species and subspecific lineages endemic to the region.

DNA studies of mountain sorrel (Oxyria digyna), a globally widespread alpine plant, also suggest there were ice-free zones for alpine species in northern B.C., possibly with connections to Beringia.⁸¹ These studies also confirm the presence of refugia on the north coast. Although it is not known to what extent low-elevation sites were included in the refugia, the studies indicate a potentially high level of genetic diversity and globally unique biodiversity in the region.

Despite the existence of refugia, a key feature of the last glacial interval is that B.C. had no extensive conifer forests as we know them today, though scattered coniferous trees (e.g., subalpine fir [Abies lasiocarpa] at high elevations in the south and lodgepole pine [Pinus contorta var. latifolia] along the coast) may have persisted. ^82,83,84 The province's modern forest ecosystems developed during the past 14,000 years, as ice-age climates ended.

In the nearshore marine environment, sea levels fluctuated widely for several thousand years and the present-day coastal marine zone was exposed to a depth of more than 100 m. Many now-isolated land masses, such as Haida Gwaii/Queen Charlotte Islands, were connected to the mainland, facilitating migrations.⁸⁵

1.4.4 end of the ice age: 14,000 to 10,000 years ago

Landscape instability continued for at least 4,000 years as the glacial regime ended between 14,000 and 10,000 years ago. During this interval of widespread climatic and ecological adjustment, extensive migrations took place throughout the region and forest ecosystems began to re-form.⁸⁶

Three broad migration patterns were superimposed over the unique alpine and coastal ecosystems that had survived glaciation in B.C. In the north, elements of the Beringian steppe-tundra landscape spread southward. From the south, migration occurred on two fronts: one along the coastal zone, largely involving coastal temperate rainforest species; and one east of the Coast-Cascades mountain axis, involving Great Basin cold steppe and dry forest species. In addition, continental boreal and conifer woodland species came from the southeast along the waning Laurentide ice sheet.⁸⁷

In some respects, the ecosystems of this transition time might have looked familiar, though out of place to modern observers. For example, for several thousand years, open, dry, cold lodgepole pine forests extended along the B.C. coast to Alaska, forming a distinctive biome.88 In the interior, cold sagebrush and grassland ecosystems likely predominated.89 Tundra-like ecosystems spread across the north of the province. Moist, cool mixed-coniferous forests featuring mountain hemlock developed for about a thousand years (12,000 to 11,000 years ago), from the pine biome along the coast down to present-day sea level.⁹⁰ These ecosystems reflected the cooler-than-present climates of the day.

In one major respect, however, life in the late-glacial period differed from what we see today, as it included the now-extinct megafauna. Mastodons (Mammut americanum), giant bison (Bison antiquus), woolly mammoths and giant ground sloths (Megatherium americanum) roamed parts of B.C., including southern Vancouver Island.⁹¹ These animals clearly influenced the ecological processes, structure and composition of plant communities. In addition, a new species - humans - began to depend upon and influence B.C.'s evolving biological diversity.

In the freshwater realm, a degree of stability returned as the land was stabilized by vegetation. Familiar ecosystems, such as cattail (Typha spp.) and bulrush (e.g., Scirpus spp.) marshes and shallow-water communities, developed widely. Lime-rich, marl-depositing ecosystems occurred widely on parts of the south coast and in the southern interior. The marine zone was, however, much less stable because of sediment input from waning valley glaciers and the invasion of salt water on a glacially depressed landscape. Diverse cold-water mollusc faunas predominated.⁹²

Between 11,000 and 10,000 years ago, a brief, but profound cooling event (called the Younger Dryas in Europe), brought cold, dry conditions for about 500 years and widely disrupted the landscape.⁹³ Temperatures declined over a few decades by as much as 5°C and cold-climate processes such as solifluction (the slow, downslope movement of moist or saturated, seasonally frozen, surficial material and soil) disturbed the landscape as far south as Vancouver Island.⁹⁴ There was widespread forest loss and return of cold and unstable ecosystems, creating alder (Alnus spp.) scrub along the coast.⁹⁵ Migration and extinction of the ice-age megafauna took place globally. As far as scientists know, none of the megafauna survived the dramatic climatic and ecological changes into the Holocene Epoch and non-glacial climates in B.C.,⁹⁶ as hunting by humans hastened the disappearance of these species.⁹⁷

1.4.5 Warm Dry Early Holocene Epoch: 10,000 To 7,000 Years Ago

Around the world, rapid warming by as much as 5-8°C ushered in the warm, interglacial climates of the modern Holocene Epoch. This period of roughly 10,000 years can be broadly divided into three climatic intervals, during which B.C.'s pre-European disturbance biodiversity arose: warm, relatively dry (from 10,000 to 7,000 years ago); warm, moist (from 7,000 to 4,000 years ago); and moderate, moist (from 4,000 years ago to the present).⁹⁸

The warm, dry early Holocene was a time of rapid immigration of species and establishment of new ecosystems in many regions under climates warmer than today. On the south coast, Douglas-fir (Pseudo-tsuga menziesii) spread widely and rapidly to dominate forests and woodlands well into the zone of today's cedar-hemlock forests.⁹⁹ In the moist climates of western Vancouver Island and the central and north coast, Sitka spruce combined with western hemlock (Tsuga heterophylla) to form an ecosystem that has no modern equivalent in B.C.¹⁰⁰

Warm, dry grasslands and Garry oak (Quercus garryana) ecosystems, including many of the species associated with them today, became established and occupied areas much greater than today. Beyond the grasslands in the southern interior, dry pine-dominated forests reached well into, if not fully occupying, today's range of the Engelmann Spruce-Subalpine fir biogeoclimatic zone.¹⁰¹ Species that are now rare in B.C., such as Oregon ash (Fraxinus latifolia), were much more widespread, whereas species common today, such as western redcedar, occurred infrequently.¹⁰² Fires burned widely in the southern half of the province, regularly disturbing the landscape in the interior and even on the coast.¹⁰³

Extensive tracts of open ecosystems related to modern non-forest communities occurred widely during the warm dry early Holocene interval. Many herbaceous and shrubby species of open terrain (e.g., sagebrush) became well established in late glacial times, especially during drier phases. To these were added species that migrated from the south following newly available warm to hot, dry valley bottoms and slopes, each according to its natural rate of dispersal. In the southern interior, valley-bottom grasslands stretched through a series of elevation zones upslope into alpine heights, forming a large area suitable for rangeland dwellers.^104,105 Extensive steppe ecosystems reached as far north as the latitude of Quesnel. Along the south coast, sea levels were at least 10 m lower than today and many coastal meadow species that are now uncommon, restricted or rare spread throughout the Georgia Basin.¹⁰⁶ Treelines were at higher elevations than today and the alpine region was less extensive in the south.

What little is known about northern ecosystems during the warm, dry interval indicates that boreal-like forests involving spruces gradually developed and pines migrated into the region. Yet even in northeastern B.C., grasslands were more widespread than today.¹⁰⁷

Freshwater environments were generally warmer and shallower than today, with some smaller water bodies being ephemeral.¹⁰⁸ Water chemistry tended toward neutral or even alkaline and marl-depositing communities occurred widely in the southern interior. Marshes and swamps were dominant types of wetlands.

Little is known about conditions in the marine environment during this interval. Whereas the early Holocene was a time of migration and connection on the south coast, isolation and fragmentation took place on the north coast. Sea levels rose and separated Haida Gwaii/Queen Charlotte Islands from the continent, drowning extensive low-lying coastal ecosystems and eventually resulting in an island area much smaller than exists today.¹⁰⁹

1.4.6 Warm Moist Middle Holocene Epoch: 7,000 To 4,000 Years Ago

Increasing moisture and gradual cooling fostered major ecological changes between 7,000 and 4,000 years ago.¹¹⁰ During this transition to modern conditions, western hemlock and Sitka spruce coastal forests persisted, while amabilis fir (Abies amabilis) and western redcedar became more abundant. Dry south coast regions continued to support Douglas-fir-dominated ecosystems, except on southeastern Vancouver Island, where there were extensive tracts of Garry oak woodland and meadow.¹¹¹

Grasslands were widespread in the southern interior, but pine forests expanded to lower elevations. Engelmann spruce (Picea engelmannii)-subalpine fir forests began to appear in moist, cool sites, while boreal forest continued to develop in the north.¹¹²

Topographic basins filled with greater amounts of permanent water.¹¹³ Ephemeral and small ponds expanded into lakes. Seasonally intermittent streams may have become permanent water courses. The wet shore zone accordingly expanded outwards and the volume of deep water grew. The marine shoreline and its ecosystems now began to stabilize, but major sea-level adjustments continued.¹¹⁴

1.4.7 Moderate And Moist Late Holocene Epoch: 4,000 Years Ago To Present

The latter part of the Holocene Epoch saw cooler temperatures than in the preceding 6,000 years, which, combined with relatively abundant moisture, fostered forest and wetland expansion. During this period, the modern pattern of ecosystems became well established and glaciers and ice fields expanded widely at high elevations.

On the coast, the most important event was the spread of western redcedar and the development of modern coastal temperate rainforests.¹¹⁵ The range of dry ecosystems, such as the Garry oak meadow complex, became very limited, although regular burning by First Nations may have maintained them over a wider area than the climate dictated.¹¹⁶ In the interior, cedar-hemlock forests arose for the first time.^117,118 At high elevations in the interior, cold, moist Engelmann spruce-subalpine fir forest became well established, largely developing from earlier, relatively dry pine forests.¹¹⁹ Similarly, coastal mountain hemlock forests developed fully and spread more widely.^120,121 In the central interior, sub-boreal spruce forests spread southward into areas previously too dry to support them. As forests expanded on many fronts, grasslands shrank to their minimum range, where they largely remain today.¹²²

Associated with the cooling and moistening climate of 4,000 years ago, fire activity declined notably. Nevertheless, fires were used by First Nations throughout much of the province and at all elevations for maintaining resources associated with open and successional communities.¹²³

Increasing moisture on the landscape fostered widespread growth of peatlands. Bogs arose or spread widely in wet coastal forests and in moist interior areas, providing habitat for the distinct species associated with them. Other wetland and aquatic habitats also expanded. Mid- and high-elevation lakes and streams cooled as glaciers redeveloped and expanded.¹²⁴

Relative stability on land was paralleled by stability in the marine zone as sea levels reached equilibrium following nearly 10,000 years of postglacial adjustment.¹²⁵

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