Connectivity is defined as the maintenance of lateral, longitudinal, and vertical pathways for biological, hydrological, and physical processes (Annear, 2004). It refers to the flow, exchange, and pathways that move organisms, energy, and matter throughout the watershed. The most obvious example of connectivity may be the free flow of water downstream in a river and the passage of fish upstream. The construction of a high dam across a stream is a vivid and obvious illustration of fragmentation or the loss of connectivity.
This exchange of energy, nutrients and material does not stop at the water's edge, it can be observed at many scales throughout the surrounding landscape. Complex, interdependent processes are continuously present throughout the watershed landscape and are required to maintain the ecological health of the system as a whole.
Explore the Connectivity Health Scores to see a series of index values that show health trends in the connectivity of ecological systems in Minnesota.
Connectivity refers to the flow, exchange and pathways that move organisms, energy and matter throughout the watershed system. These interactions create complex, interdependent processes that vary over time.
For example, the stream continuum concept describes stream connectivity in four dimensions (Annear, 2004).
- longitudinal – linear connectivity
- lateral – floodplain connectivity
- vertical – hyporheic (below the stream bed)
- temporal (time) – many scales; seasonal, multiyear, generational
Within the stream system, longitudinal connectivity refers to the pathways along the entire length of a stream. As the physical gradient changes from source to mouth, chemical systems and biological communities shift and change in response. The River Continuum Concept (RCC) can be applied to this linear cycling of nutrients, continuum of habitats, influx of organic materials, and dissipation of energy.
- A headwater woodland stream has steep gradient with riffles, rapids and falls.
- Sunlight is limited by overhanging trees, so photosynthesis is limited.
- Energy comes instead from leaves and woody material falling into the stream
- Aquatic insects break down and digest the terrestrial organic matter.
- Water is cooled by springs and often supports trout.
In the mid-reaches,
- The gradient decreases and there are fewer rapids and falls.
- The stream is wider, sunlight reaches the water allowing growth of aquatic plants.
- Insects feed on algae and living plants.
- Proportion of groundwater to runoff is lower so stream temperatures are warmer.
- The larger stream supports a greater diversity of invertebrates and fish.
The river grows and the gradient lessens with few riffles and rapids.
- Terrestrial organic matter is insignificant in comparison to the volume of water
- Energy is supplied by dissolved organic material from upstream reaches.
- Drifting phytoplankton and zooplankton contribute to the food base as does organic matter from the floodplain during flood pulses.
- Increasing turbidity reduces sunlight to the streambed causing a reduction in rooted aquatic plants.
- Backwaters may exist where turbidity has settled and aquatic plants are abundant.
- Fish species are omnivores and plankton feeders such as carp, buffalo, suckers, and paddlefish.
- Sight feeders are limited due to the turbidity (Minnesota DNR, Healthy Rivers).
Lateral connectivity refers to the periodic inundation of the floodplain and the resulting exchange of water, sediment, organic matter, nutrients, and organisms. Lateral connectivity becomes especially important in large rivers with broad floodplains.
Periodic floods refill oxbow lakes and recharge wetlands. Inundated areas may be used as spawning areas by species such as northern pike. Floodwaters carry nutrients and organic matter from the land to the stream's aquatic plants, plankton, stream invertebrates, and fish. Seasonal flooding produces a variety of streamside vegetation and habitat for a diversity of birds and mammals (Minnesota DNR, Healthy Rivers).
Access to floodplain is also important for small streams that can experience dramatic episodic flooding. Heavy, localized rains can cause small streams to rise several feet in a few hours. This flashiness is largely a result of more overland flow and less infiltration following the conversion of native land cover to row crops and human communities. Large amounts of sediment are mobilized by these events, impacting all trophic levels and altering biological communities in the stream and the adjacent floodplain.
Vertical connectivity is represented by the connection between the atmosphere and groundwater. The ability of water to cycle through soil, river, and air as liquid, vapor, or ice is important in storing and replenishing water. This exchange is usually visualized as unidirectional–precipitation falling onto land and then flowing over land or percolating through the ground to the stream.
An equally important transfer of water occurs from the streambed itself to surrounding aquifers. Groundwater can contribute to flows in the river at certain times in the year and at certain locations on the same stream. Streams may either gain or lose water to the surrounding aquifer depending on their relative elevations. Lowering the water table through groundwater withdrawals may change this dynamic exchange in unanticipated ways (Stream Corridor, FISRWG).
The slow movement of water through sediments to the river produces several ecological benefits.
- The water is filtered of many impurities.
- It usually picks up dissolved minerals.
- The water is cooled.
- The water is metered out slowly over time.
This is particularly important in smaller, cooler streams for the maintenance of critical habitat for fish, wildlife and invertebrate species.
A stream exhibits temporal connectivity of continuous physical, chemical, and biological interactions over time, according to a rather predictable pattern. These patterns and continuity are important to the functioning of the ecosystem. Over time, sediment shifts, meanders form, bends erode, oxbows break off from the main channel, channels shift and braid. A stream rises and falls according to seasonal patterns, depending on rain and snowmelt. Throughout most of Minnesota, free-flowing rivers experience high water in spring, falling flows in summer, moderate flows in fall, and base flows in winter. The watershed has adjusted to these normal fluctuations, and many organisms have evolved to depend on them (Minnesota DNR, Healthy Rivers).
Landscape connectivity is 'the degree to which the landscape facilitates or impedes movement among resource patches' (Taylor et al, 1993). Biological components - both plant and animal – must have access to all the habitats necessary for all stages of their life cycle. This includes both physical and temporal access to habitats. For example, the need for seasonal timing is acute for many wildlife species to accommodate breeding, reproduction, and migration. For plant species it is equally important for dispersal, growth and competition.
Landscape connectivity has two components:
- Structural connectivity – the spatial structure of a landscape that can be described from map elements
- Functional connectivity – the response of individuals to landscape features (Brooks).
Habitat does not need to be structurally connected in order to be functionally connected. Some organisms have the ability to bridge the gaps between habitat patches and can link resources by crossing over uninhabitable or partially inhabitable locations (Taylor, 2006). For example, a neotropical migrant bird will perceive a landscape as connected across a greater range than would a salamander restricted to moist forest floors (With). “These movements… of individuals, materials, nutrients, energy or disturbances… are affected by how (habitat) patches are arrayed in the mosaic…. Although landscape connectivity is often thought of in terms of corridors - roughly linear strips of habitat connecting otherwise isolated habitat patches – connectivity is in fact a complex product of:
- patch quality (e.g. resistance to movement or patch-residence time)
- boundary properties ...
- the movement characteristics of the features of interest” (Weins).
As people use the land, the natural landscape is divided into ever-smaller pieces by elements like railways, utility lines, roads, houses, and parking lots. The remaining natural areas, or fragments, are reduced in size and degraded in quality, resulting in a decline in plant and animal populations, and the disappearance of some sensitive animal species and plant communities.
How does fragmentation impact the environment? (from Minnesota DNR Natural Resource Guide,"Changes to the Land")
- Fragmentation results in a dramatic increase in 'edge' habitat, which provides increased access to the more protected interior habitats by predators, including domestic animals.
- Fragmentation creates barriers to wildlife movement, and is especially harmful to reptiles and amphibians that depend on the ability to move between their aquatic habitats and upland areas.
- Fragmentation creates opportunities for harmful exotic plant species to invade. Many exotic species can out-compete native plant communities and often provide little or no habitat value.
- Because it's associated with human activity, fragmentation often brings pesticides, noise, lights, and other pollutants and disturbances that can profoundly impact a species' ability to function.
"Uunganisho ni ""kuhifadhi njia za upande, longitudinal, na wima kwa michakato ya kibiolojia, hydrological, na kimwili.""" Linarejelea mtiririko, kubadilishana, na njia ambazo husafirisha viumbe, nishati, na vitu kotekote katika eneo la maji. Mfano wa wazi wa uhusiano wa maji ni mtiririko wa maji chini ya mto na mtiririko wa samaki juu ya mto. Ujenzi wa bwawa la juu juu ya kijito ni mfano wa wazi wa kugawanyika au kupoteza uhusiano. Mabadiliko haya ya nishati, virutubisho na vifaa hayasimami kwenye ukingo wa maji, yanaweza kuchunguzwa kwa viwango vingi katika mazingira yote yanayozunguka. Utaratibu tata, unaohusiana unaendelea katika mazingira yote ya maji na inahitajika kudumisha afya ya ikolojia ya mfumo kwa ujumla. "Kuchunguza ""Connectivity Health Scores"" ni orodha ya viwango vya afya vinavyoonyesha mwenendo wa afya katika uhusiano wa mifumo ya ikolojia ya Minnesota." Uunganisho ni mtiririko, kubadilishana na njia ambazo husafirisha viumbe, nishati na vitu katika mfumo wa maji. Maingiliano hayo huunda michakato tata, inayohusiana ambayo hutofautiana kadiri wakati unavyopita. Kwa mfano, dhana ya mkondo wa mkondo inaelezea muunganisho wa mkondo katika vipimo vinne (Annear, 2004). - longitudinal <unk> linear connectivity - lateral <unk> floodplain connectivity - vertical <unk> hyporheic (chini ya kitanda cha mkondo) - temporal (wakati) <unk> mizani mingi; msimu, multiyear, kizazi Ndani ya mfumo wa mkondo, longitudinal connectivity inahusu njia kando ya urefu wote wa mkondo. Kadiri gradient ya kimwili inavyobadilika kutoka chanzo hadi kinywa, mifumo ya kemikali na jamii za kibiolojia hubadilika na kubadilika kwa kujibu. Mfumo wa Mtiririko wa Mto (RCC) unaweza kutumika kwa mzunguko huu wa mstari wa virutubisho, mzunguko wa makazi, mtiririko wa vifaa vya kikaboni, na kupotea kwa nishati. - Mto wa misitu ya kichwa cha maji una mteremko mkali na riffles, rapids na maporomoko. - Nuru ya jua hupunguzwa na miti iliyoinuka, kwa hiyo fotosynthesis hupunguzwa. - Badala yake, nishati hutoka kwenye majani na mbao zinazokuwa zikianguka kwenye kijito - Wadudu wa majini huvunja na kumeng'enya vitu vya kikaboni vya ardhini. - Maji hu baridiwa na chemchemi na mara nyingi hutegemeza samaki aina ya trout. Katika katikati ya kufikia, - gradient hupungua na kuna rapids chache na kuanguka. - Mto ni mpana, nuru ya jua hufikia maji kuruhusu ukuaji wa mimea ya majini. - Wadudu hula mwani na mimea iliyo hai. - Uwiano wa maji ya chini ya ardhi kwa mtiririko ni chini hivyo joto mkondo ni joto. - Mto mkubwa hutegemeza utofauti mkubwa zaidi wa wanyama wasio na uti wa mgongo na samaki. Mto huo hukua na mteremko wake hupungua kwa kuwa kuna miamba na maporomoko machache. - Vitu vya kikaboni vya ardhini ni vidogo ikilinganishwa na kiasi cha maji - Nishati hutolewa na vitu vya kikaboni vilivyomwagika kutoka juu ya mto. - Drifting phytoplankton na zooplankton kuchangia msingi wa chakula kama vile ana suala la kikaboni kutoka floodplain wakati wa msukumo wa mafuriko. - Kuongezeka kwa ukungu hupunguza mwangaza wa jua kwenye kitanda cha mto na kusababisha kupungua kwa mimea ya majini yenye mizizi. - Maji ya nyuma ya maji yanaweza kuwepo mahali ambapo ukungu umekaa na mimea ya majini ni nyingi. - Spishi za samaki ni omnivores na plankton feeders kama vile carp, nyati, suckers, na paddlefish. - Sight feeders ni mdogo kutokana na turbidity (Minnesota DNR, Mito ya Afya). Uunganisho wa upande unarejelea mafuriko ya mara kwa mara ya eneo la mafuriko na kubadilishana kwa maji, matope, vitu vya kikaboni, virutubisho, na viumbe. Uunganisho wa upande unakuwa muhimu hasa katika mito mikubwa yenye maeneo mapana ya mafuriko. Mafuriko ya mara kwa mara hujaza tena maziwa ya oxbow na kuijaza tena maeneo yenye unyevunyevu. Maeneo yaliyofurika yanaweza kutumiwa kama maeneo ya kuzaa kwa spishi kama vile pike ya kaskazini. Maji ya mafuriko hubeba virutubisho na vitu vya kikaboni kutoka ardhini hadi kwa mimea ya majini, plankton, wanyama wasio na uti wa mgongo, na samaki. Mafuriko ya msimu hutokeza mimea mbalimbali ya kando ya mito na makao ya ndege na mamalia mbalimbali (Minnesota DNR, Mito yenye Afya). Upatikanaji wa eneo la mafuriko pia ni muhimu kwa vijito vidogo ambavyo vinaweza kupata mafuriko makubwa ya vipindi. Mvua kubwa ya mahali fulani yaweza kusababisha vijito vidogo viongezeke kwa meta kadhaa katika muda wa saa chache tu. Hii flashiness ni kwa kiasi kikubwa matokeo ya zaidi ya ardhi mtiririko na chini ya infiltration kufuatia uongofu wa asili ya ardhi kifuniko kwa safu mazao na jamii za binadamu. Mzunguko huo unaathiri viwango vyote vya chakula na kubadilisha jamii za kibiolojia katika kijito hicho na eneo la mafuriko lililo karibu. Uunganisho wa wima unawakilishwa na uhusiano kati ya anga na maji ya chini ya ardhi. Uwezo wa maji kuzunguka-zunguka katika udongo, mito, na hewa kama umajimaji, mvuke, au barafu ni muhimu katika kuhifadhi na kurudisha maji. Kubadilishana hii ni kawaida visualized kama unidirectional <unk> mvua kuanguka juu ya ardhi na kisha mtiririko juu ya ardhi au percolating kupitia ardhi kwa mkondo. Uhamisho wa maji wenye umuhimu sawa hutokea kutoka kwenye kitanda cha mto wenyewe hadi kwenye matope ya maji yanayozunguka. Maji ya chini ya ardhi yanaweza kuchangia mtiririko wa maji katika mto wakati fulani wa mwaka na katika maeneo fulani kwenye mto huo. Mito inaweza kupata au kupoteza maji kwa aquifer ya karibu kulingana na urefu wao wa jamaa. Kuondoa maji ya chini ya ardhi kwa kuchukua maji ya chini ya ardhi kunaweza kubadilisha kubadilishana kwa nguvu kwa njia zisizotarajiwa (Stream Corridor, FISRWG). Mzunguko wa polepole wa maji kupitia matope hadi kwenye mto hutoa faida kadhaa za kimazingira. - Maji hayo yamechujwa kutokana na uchafu mwingi. - Kwa kawaida huchukua madini yaliyoyeyushwa. - Maji yamebadilika. - Maji hupimwa polepole kadiri wakati unavyopita. Hii ni muhimu hasa katika mito midogo, baridi kwa ajili ya kudumisha makazi muhimu kwa ajili ya samaki, wanyama wa porini na spishi za invertebrate. Mtiririko huonyesha uhusiano wa muda wa mwingiliano wa kuendelea wa kimwili, kemikali, na kibiolojia kwa muda, kulingana na muundo unaotabirika. Mifumo hiyo na kuendelea kwake ni muhimu kwa utendaji wa mfumo wa ikolojia. Baada ya muda, mchanga hubadilika, miamba hufanyizwa, miundo huharibika, miamba ya ng'ombe huvunjika kutoka kwenye mfereji mkuu, mifereji hubadilika na kuunganishwa. Mto huinuka na kushuka kulingana na misimu, ikitegemea mvua na kuyeyuka kwa theluji. Katika sehemu kubwa ya Minnesota, mito inayotiririka kwa uhuru hupata maji mengi wakati wa majira ya kuchipua, maji ya chini wakati wa kiangazi, maji ya wastani wakati wa vuli, na maji ya chini wakati wa majira ya baridi kali. Mto huo umebadilika kulingana na mabadiliko hayo ya kawaida, na viumbe wengi wamebadilika ili kutegemea maji hayo (Minnesota DNR, Healthy Rivers). "Uunganisho wa mazingira ni ""kiwango ambacho mazingira huwezesha au kuzuia harakati kati ya patches rasilimali"" (Taylor et al., 1993)." Vipengele vya kibiolojia - mimea na wanyama <unk> lazima kuwa na upatikanaji wa makazi yote muhimu kwa hatua zote za mzunguko wao wa maisha. Hii inajumuisha wote kimwili na muda upatikanaji wa makazi. Kwa mfano, aina nyingi za wanyama-pori huhitaji sana wakati wa majira ili waweze kuzaliana, kuzaliana, na kuhama-hama. Kwa spishi za mimea ni muhimu sawa kwa ajili ya kuenea, ukuaji na ushindani. Mawasiliano ya mazingira ina vipengele viwili: - Mawasiliano ya muundo <unk> muundo wa nafasi ya mazingira ambayo inaweza kuelezwa kutoka kwa vipengele vya ramani <unk> Mawasiliano ya kazi <unk> majibu ya watu kwa vipengele vya mazingira (Brooks). Habitat haihitaji kuwa na muundo uliounganishwa ili kuwa na muundo uliounganishwa. Baadhi ya viumbe wana uwezo wa kuunganisha mapengo kati ya patches ya makazi na wanaweza kuunganisha rasilimali kwa kuvuka juu ya maeneo yasiyo ya makazi au sehemu ya makazi (Taylor, 2006). Kwa mfano, ndege wa kusafiri wa neotropical ataona mazingira kama kushikamana katika mbalimbali kubwa kuliko ingekuwa salamander mdogo kwa sakafu ya msitu unyevu (Na). Hizi harakati... za watu, vifaa, virutubisho, nishati au usumbufu... zinaathiriwa na jinsi (makazi) patches ni arrayed katika mosaic.... Ingawa uhusiano wa mazingira mara nyingi hufikiriwa katika suala la vijia - karibu mistari ya makazi inayounganisha patches za makazi zilizotengwa <unk> uhusiano kwa kweli ni bidhaa tata ya: - ubora wa patch (kwa mfano upinzani kwa harakati au patch-wakati wa makazi) - mali ya mpaka... - harakati sifa ya vipengele vya maslahi <unk> (Weins). Watu wanapotumia ardhi, mandhari ya asili hugawanywa katika vipande vidogo-vidogo na vitu kama vile reli, mistari ya huduma, barabara, nyumba, na maegesho. Sehemu za asili zilizobaki, au vipande, hupunguzwa kwa ukubwa na kuharibika kwa ubora, na kusababisha kupungua kwa idadi ya mimea na wanyama, na kutoweka kwa baadhi ya spishi za wanyama nyeti na jamii za mimea. Uvunjaji-mvua huathirije mazingira? "Kutokana na mabadiliko ya mazingira, sehemu ya ardhi ya Minnesota imeharibiwa na ""mipaka"" ya mazingira, ambayo hutoa upatikanaji wa zaidi wa mazingira ya ndani ya wanyama wa kuwinda, ikiwa ni pamoja na wanyama wa nyumbani." - Fragmentation inaunda vizuizi kwa harakati ya wanyama wa porini, na ni hasa madhara kwa wanyama wa kutambaa na amphibians ambayo hutegemea uwezo wa kusonga kati ya makazi yao ya majini na maeneo ya juu. - Ugawanyiko huo hufanyiza fursa za kuvamia mimea ya kigeni yenye kudhuru. Spishi nyingi za kigeni zinaweza kushindana na jamii za mimea ya asili na mara nyingi hutoa thamani ndogo au hakuna thamani ya makazi. Kwa sababu ni kuhusishwa na shughuli za binadamu, fragmentation mara nyingi huleta dawa za kuua wadudu, kelele, taa, na uchafuzi mwingine na usumbufu ambao unaweza athari kubwa ya uwezo wa spishi ya kufanya kazi.