Terrestrial ecosystems around the world range from hot, dry deserts and cold tundra regions which have a low diversity of life to wet, tropical rainforests rich in life.
All terrestrial ecosystems are classified with respect to the vegetation type located there. Temperature, precipitation, and soil characteristics are therefore important to how we describe these ecosystems. The following are the characteristics of five general biome types, but there may be many more depending on the classification scheme used:
Tropical rainforests have annual precipitation values greater than 200 cm and annual average temperatures greater than 24° C. They are composed of large deciduous trees with a huge variety of plants and animals.
Temperate deciduous forests have annual precipitation values between 50 and 200 cm and annual average temperatures range between 12° C and 25° C. They are composed of a mixture of deciduous and coniferous trees.
Grasslands have annual precipitation values between 25 and 75 cm and annual average temperatures range between 4° C and 29° C. They are composed of a wide variety of tall grasses and grazing animals.
Boreal forests have annual precipitation values between 50 and 240 cm and annual average temperatures range between 1° C and 15° C. They are composed of mostly coniferous trees and shrubs.
Tundra has an annual precipitation value between 5 and 100 cm and annual average temperatures range between -9° C and 3° C. It is composed of small low growing shrubs and grasses adapted to the extreme cold.
What happens to the temperature at higher latitudes? The temperature decreases as you move north or south of the equator. As a result biomes are also aligned in a north-south pattern, just as the early naturalists and explorers observed that the distribution of plants and animals was in distinct patterns and not random.
Canada is divided into 15 terrestrial and 5 marine ecozones. An ecozone is an ecological classification system based on climate, landforms, wildlife, vegetation, soils, drainage, and human use.
The biggest threats to terrestrial ecosystems are habitat loss due to deforestation, urban expansion, and pollution destruction. Deforestation will directly remove vegetation and alter the abiotic characteristics of the area because of more sunlight reaching the ground. It will also increase the wind intensity, and create increased runoff from precipitation that is no longer absorbed by the trees. This leads to nutrients washing away and, most importantly, the habitat of many animal species disappearing.
In addition to habitat loss, climate change is altering the patterns of many species as they try to adapt or shift their ranges. Invasive species, including the Asian long-horned beetle and spruce budworm, are also a threat to terrestrial ecosystems because they destroy forests annually.
A community is all of the populations of different species that interact within a defined ecosystem. Biodiversity is the variety of different types of species in a community. It includes variation in the types of species, genetics within a species, and the interactions between the species in an ecosystem. The three levels of biodiversity are:
Genetic diversity is the variation present at the level of the gene. Genes are the building blocks that determine how an organism will develop. Genetic diversity is important because it represents the raw material for evolution and adaptation.
Species diversity represents the number of different unique organisms (species). The niche of a species refers to its specific role in the behaviour of an ecosystem. All species are important because each one will have a specific role in keeping the ecosystem functioning. For example, if all of the bees (its niche being a pollinator) were to disappear, many plants would not be pollinated and would not reproduce.
Ecosystem diversity represents the species distributions, community patterns, and the role of the species including their interactions within ecosystems. Different ecosystems are important for different specialist species. For example, the monarch butterfly requires milkweed as a food source, therefore if the milkweed habitat were lost then the monarch butterflies would disappear.
Value of Biodiversity
Biodiversity is priceless. With every species lost, the opportunity to understand the possible benefits that species may have brought the ecosystem is lost as well. The following summarizes some of the importance of biodiversity:
genetic diversity in plants allows breeders to select for traits (e.g., larger fruit)
genetic diversity allows species to adapt to changing conditions
more foods for humans and other animals (e.g., variety of vegetables and fruits)
medicines (an estimated 3 billion people rely on medicines from plants)
economic activity (harvesting of natural resources)
destruction of insects removes natural pest controls (e.g., spiders help control mosquito populations)
What was the first thought that came to your mind when you read the title above? Most people believe that human exploitation (hunting, fishing, etc.) is the main cause of species extinctions. Although hunting is believed to have resulted in the extinction of many species such as the mammoth, dodo, and passenger pigeon, it is not the primary cause. Instead, it is the loss of habitat caused by an expanding population building roads, expanding city limits, and cutting down forests for agricultural land that is affecting the biodiversity in ecosystems.
Two international policies help to protect biodiversity.
The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) was created in 1973 to target poaching, smuggling, and the illegal trade of species. The United Nations Convention on Biological Diversity was created in 1992 to the promote co-operation among countries with the goal of conserving biodiversity.
The Canadian National Parks Act was developed in 1911 to protect areas of nationwide significance and for public understanding and appreciation of the natural environment. In 2004 the Species at Risk Act (SARA) went into effect prohibiting the killing of species listed under the act and preventing the destruction of their critical habitat.