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From the human dimension, conservation has the following aspects:

• preventing problems: the cheapest and most effective way is to prevent problems from occurring, by applying foresight. However, this method gains little support, because the need for this type of action cannot be demonstrated. People become motivated only when a threat can be seen, particularly when it affects them already.
• knowing the laws: conservation is against unplanned development that breaks ecological as well as human laws. Problems can be predicted by knowing the laws of ecology and how a project breaks such laws. This is still a form of prevention, but difficult to win in court, since ecological laws are not part of human laws.
• finding solutions: once problems have arisen, solutions must be found. As shown in the article on resource management, solutions have several dimensions, leading all the way back to human need. Finding lasting and efficient solutions requires smart thinking. This aspect finds support easily, but requires high expenses and guarantees only limited success.
• adjusting demand: adjusting demand below the natural replenishment cycles or finding alternative sources and substitutions. This complex issue is particularly relevant to fishing. Ironically, the availability of a substitute resource (another fish species), often leads to the complete depletion of the first species.
• setting aside for now: concessions can often be won easily as part of a new development. Keen on going ahead with the profitable venture, developers often conceed easily to conservation demands to set aside samples of undisturbed natural communities, areas for recreation, and so on.
• setting aside for tomorrow: setting aside for our children should find easy support because everyone has children and has altruistic behaviour towards them, in order to survive as a species. However, support for someone else's children, is not easily forthcoming. We should set aside for the future: use, enjoyment, scientific discovery (archaeological sites), even oil fields for purposes as yet unknown.

Likewise, conservation, the weapon against the decline of life, must attack from all possible angles. Take for instance the example just mentioned. Note that the causes (habitat loss + predation + disease + collection) are all independent factors, which means that none is influenced by any of the others. An improvement of 20% to each would lead to 1.2 x 1.2 x 1.2 x 1.2 = 2.07, or a 107% improvement! Quite high a success for such a moderate effort. Thus identifying all causal factors is important in solving environmental problems.

Conservationists should be warned for people's knee-jerk reaction, wanting to throw the baby out with the bath water. The present solutions are discredited entirely, and something new and unproven is put in its place. Always analyse what is good of the present situation or solution and what is not. Then maximise the good things while minimising the bad ones. How far we wish to go, depends on our vision of what we wish to achieve: free plunder or paradise?
 
 

From pillage to paradise Conservation can be practised on a scale from plunder (take all) to paradise (leave all). It has consequences for the environment, different ways to go about it, and it has different levels of public support. The idea is discussed here relating to the sea, because this a large resource is exploiteded almost exlusively by extraction.

• plunder: free and unlimited access leads to rapid depletion. As fish stocks disappear, new fish stocks are found. It is the classical way of fishing an open-access commons. It requires no regulation, finds enthusiastic support from fishermen, but after collapse of the fishery, fishermen may need to be compensated or subsidised.
• sustainable exploitation: the fishery is managed to be sustainable. It requires intensive regulation, a bureaucracy to maintain and police it, subsidies from Government or the fishing industry. It finds lukewarm support from the fishing industry, which finds ways to go around the rules. It is still based on the management of single species. Old fish disappear, and so do predator species.
• balanced exploitation: the sea is fished in a balanced way, with fishing quotas aimed at retaining a functional balance in the environment. This has not been done yet. It may not be practical because even sustainable exploitation leaves stock levels too low to be functional. The method of leaving large areas fallow for many years, to be fished out in a short time, may work, but it has not been done yet. Note that area closures happened by default in World War II, and fish stocks rebounded.
• conservation but take some: many marine parks allow for extractive practices, but attempt to control these. It is a half-way solution towards protection, but it does not afford complete protection.
• no-take conservation: marine reserves are set aside with the strict rule that nothing can be taken. It allows areas to recover to (hopefully) original levels of life and diversity. Such areas can then serve to compare other areas with. They also allow for undisturbed scientific research, and they give enjoyment to those who wish to enjoy the natural environment passively. Any form of extraction is in conflict with these uses, and cannot be allowed. Such reserved areas are cheap to create and to maintain.
• paradise: the highest level of restoration is in attempting to create pristine wilderness areas in the sea (or on land). Such areas are large, and don't allow extraction of any kind, not even for scientific research. All threats to such paradises are addressed, such as mud from rivers, pollution from industry, noise pollution, threats from boats and so on. People gain access only after having done an environmental course to adapt their behaviour. Such places require proactive conservation, cost money, but will in the end be the best we can do for our children. People rise to the challenge.

• insurance: an insurance against stupidity and poor (fisheries) management because no matter how much the areas outside the reserve are depleted, the area inside will continue on as if nothing had happened, producing the larvae necessary to reestablish life on depleted grounds.
• refuge: a refuge for all kinds of organisms, large and small.
• nursing ground: inside the reserve, fish can reproduce at their leisure, and their young spill over to areas around, where they can be fished.
• natural area: because people do not meddle in the fish's affairs, species will develop into a balanced community, rich in functionality and life.
• recreation: as long as people do not disturb the life there, they are welcome for eco-tourism, recreation, diving, fish watching, photography and so on.
• research: research benefits because the scientific experiments are not disturbed. The whole area can serve as a baseline to compare other places with, in order to measure the effects of human intervention. The reserve will stabilise at maximum biodiversity and maximum biomass, which in itself is interesting, while serving as a baseline too. Scientists can study a truly natural environment.
• genetic refuge: the diversity of species embodies undiscovered genetic qualities such as medical compounds, biocides and more.
• education: people from all walks of life, and particularly school children can visit the reserve to observe wildlife and to become inspired by the conservation concept. Whereas elsewhere the environment has deteriorated, one can at least find natural life inside protected aeas.

Conservation would have been much easier had humans not been affected. The humand dimension is indeed large and unwilling.
 

The human dimension To do conservation for the benefit of nature is difficult enough, but because humans are involved in every step, the matter becomes very much more complicated. In fact, this aspect can become quite time-consuming and energy-sapping, often obscuring what the whole purpose of conservation is all about.

Human society has become more complicated over time, and will continue to do so. People have occupied every bit of land, and have also been allowed to own it. By having an interest in an area planned for conservation, or an extractable species, human lives are affected and conflicts arise. People who have a claim to be considered, call themselves stakeholders. Don't be surprised that a stakeholder can live hundreds of kilometres away from the place of conflict. Here are the human interests that need to be considered along every step:

• economic: people's incomes are affected. Countries with a Bill Of Rights (USA fifth amendment), require such people to be compensated financially. It increases the cost of conservation. However, often new opportunities present themselves, and people can get better jobs through re-training. Where fishing is stopped, boat owners and skippers can learn to earn a living from eco-tourism. Park rangers are required, and those displaced from the area make good rangers due to their local knowledge.
• rights: over time, people have given themselves all kinds of rights. Their present predicament is seen as a right obtained through custom, and any change to it is seen as an infringement of such rights.
• tradition: people have been doing what they do for many generations, often passed down in families from father to son. Villages have a tradition, and so do areas. A conservation effort may upset such traditions.
• culture: every ethnic group has a different culture. Within a culture, specific rights and beliefs are held dearly. Conservation may infringe on such cultural values.
• spiritual: persons and groups may have spiritual values, arising from beliefs and superstitions.
• emotional value: people often value a place or a species emotionally. Such values cannot be measured but are real to the beholders. A large range of emotional values can be held.
• race: racial matters may dominate conservation efforts. Original People like the Maori in New Zealand, the Aborigines in Australia and the Indians in America and Canada, have lived in the area for a long time, and have cultural and spiritual ties with an area. However, often the race issue is used to gain power and income.

stakeholder= an independent party with whom each of those who make a wager, deposits the money. A person holding an interest.
stake= a sum of money wagered on an event. An interest or concern, especially financial.
at stake= at hazard, at risk, at issue, concerned.

To illustrate the complexity of (marine) conservation, consider the number of Government departments involved in conservation issues. Note that only their functions relating to conservation have been mentioned, and that government departments may have been arranged differently in different countries:

• Environment: the main regulatory body for industry, handling of dangerous goods, environmental protection, biodiversity. Contaminated sites. State of the environment reporting. soil conservation and rivers control. Introduced organisms. Resource management.
• Conservation: the caretaker of the conservation estate: parks, reserves, national parks, marine reserves, scenic reserves, river margins and more. It provides access, tracks, huts, etc. It may charge for access, use of facilities and franchises for commercial operations. It is the executive arm of Environment, and has expertise in handling emergencies, and enforcing law. Saving endangered species. Eradicating invasive exotic species. Marine conservation.
• Parks and Reserves: the caretaker of parks and reserves, could be part of  Conservation but is in some countries a separate department.
• Fisheries: the main player in conserving the marine environment. It controls exploitation by a number of methods (See marine conservation). Quota management.
• Forestry: oversees or controls logging of exotic and native forests. Formulates policies for planting and assistance. May be involved in the forests of the conservation estate.
• Agriculture: assists farmers towards economic success with least side effects on the environment. Erosion control, fertiliser rationalisation. Biosecurity. Sustainable resource use. Organic farming.
• Arts and Cultural Heritage: manages historical places and cultural heritage. Protects sites of importance.
• Customs: to prevent illegal trade (CITES), unwanted introduction of diseases and pests (biosecurity). Manages quarantine facilities.
• Land and Survey: measures the land, produces maps & charts, which include protected aeas. Land titles. Crown land.
• Transport: shipping, civil aviation, railways, road transport and roading. A very important future player in conservation due to the fragmenting effects of transport infrastructure. Also manages response facilities for oil spills. Maritime safety. Road safety.
• Internal Affairs: develops policy, emergency services, community grants. Communication. Emergency channels.
• Energy and Minerals: parks and reserves may contain extractable resources, and these should remain accessible.
• Foreign Afairs: international relations, treaties, conferences, agreements, United Nations, trade agreements. Developing national advantage. Trade.
• Justice and Law: most conservation actions require support by law, but the trend is towards softer solutions with community cooperation and management. Making law. Administering justice. Policy advice.
• Police: Policing services. Safer communities. Law enforcement.
• Science and Technology: scientific research supporting the environment and conservation. Science funding. Consulting to Government. Coordinating science and technology.
• Education: education policy. School Curriculum. Professional training. Unit standards. Financing.
• Tourism: promoting the nation. Marketing, advertising. Ecotourism. Nature tourism.
• Original People: Crown's relationship. Treaty compliance. Law reform. Partnership. Traditional use. Culture.
• Local, District and Regional Government: the executive arms of government and its many departments.
• Parliamentary Commissioners: scrutinising the effectiveness of government departments and reporting on their findings. Suggesting new ways.

• Commercial Fishing Industry: commercial fishermen are affected by marine reserves. They may consist of several groups and local fisheries.
• Seafood Processing Industry: are usually consulted although they do not have a direct interest in marine reserves.
• Amateur Fishing Associations: cooperation is needed from all amateur fishermen for marine reserves to be successful.
• Acclimatisation Societies: these people have introduced often noxious species for the purpose of hunting. They also have a stake in rivers and lakes for trout fishing, and are interested in good water quality.
• Environmental and Conservation Organisations: these are often the driving forces behind conservation and certainly were before the United Nations became active, and national governments followed. Now that government departments are better organised and financed, with full-time officers, voluntary conservation organisations are languishing.
• Educational Institutes and Universities: many scientists work here and they are very knowledgeable in their specific fields. From this resource, often consultative committees are formed for policy advice.
• Research Laboratories: these do not only have specific knowledge, but also the means to do high level research to come up with answers to environmental problems. They are also often involved in policy advice.
• Original People: the local original people are usually organised by tribes and have strong local, regional and national interests. They are being consulted extensively.

• cultural tradition: It is a tradition of hundreds of years, laid down in our culture. We can't give that up.
• we've never had restrictions: We are reponsible people. We don't need restrictions. Let us sort this out. The sea is free.
• nothing has changed: The situation is not worse than last year or the year before. Why worry?
• there's plenty still: Fishing has its ups and downs. The good years make up for the losses. Next year will be better. The fish have only become smarter. We need bigger gear and faster boats.
• it is our living: Why take our living away? What are we to do next?
• why here?: There are plenty of alternatives. Why here? Not in my backyard.
• it is someone else's fault: Why should we get penalised here for the problems elsewhere?

• We've always done it this way.
• I didn't like rules. When the fishing is good, you have to take all you can get.
• I didn't notice. I was too optimistic.
• I didn't heed the clear warning signs.
• We needed the money.
• I wanted to fish close to home.
• It  was the Government's fault. They should have done something a long time ago.

(In class, I often let children (10-16 years old) decide on this, and it is amazing to see how unanimously condemning they are of such excuses)
 
 
 

Ten dilemmas Scientists Elliott and Lawrence, looked at conservation in a critical way, questioning the presumed validity of conservation practices and values. These are mentioned here to illustrate some scientists' misgivings, and they are annotated by Floor Anthoni:

• Should conservation focus on quality (structure and functioning of the environment) or quantity? Very relevant. Biodiversity is part of quality, and when it is found to be high, one may assume (!) higher structure and functioning as well. However, quantity is easier to measure. One mistake made with marine reserves is that the quantities of some exploited species are measured, then used as an argument that reserves work. However, the decline of dozens to hundreds of other species is neither noted, nor measured.
• Which species should be protected and why? Conservation is usually pushed for either economic reasons or feel-good reasons.  Thus commercially important species and cute animals have priority. Ignorance about all others condemns them. However, all species deserve protection.
• Ecology and evolution are dynamic, and extinctions part of it. If evolution means the total dominance of Earth by Man, then the Man-made extinctions are part of it, and so is the consequential fall of civilisation and decline of Man as a species. However, if Man is considered an intelligent caretaker, aiming for sustainable existence and co-existence with nature, and for his own survival, then extinctions must be prevented. Since Man has the power to destroy, it has become a matter of how he views the world.
• How to assess a species' or habitat's conservation value? The only values we know are human values. Our ignorance of ecology prevents us from being able to assess and assign natural values. Because of this, conservation may be doomed to remain a hit-and-miss affair. But the factors contributing to nature's resilience, as explained in biodiversity, may guide us.
• Should we use flagship species to protect others? (otter versus seaweed habitat) Should we do the right thing for the wrong reasons? Should we deceive the public, or spend more on education in order to gain political support? However, as conservation becomes more and more a political football, politicians will use any means to justify the ends.
• Is our aim to protect the current status quo, or allow it to fluctuate over time? Very important question. Is the current status a depleted, degraded environment? Why protect it? We expect a (marine) nature park to improve over time, but will it do so? If the causes for its degradation are not taken away, then why protect it? Design nature reserves such that they have a good chance of improving over time, otherwise don't have them and don't mislead the public about them.
• What changes are we prepared to accept? Natural changes are neither good, nor bad. They fluctuate, and nature has adjusted to cope with these. However, human-induced changes are mostly bad, and getting worse, and nature has not evolved to cope. Nature parks are precious concessions by society, and they are scarce. So we have to make sure they work, and that changes are only making them better.
• Marine areas are more resistant to change, but depend on areas outside, often in other countries. True and false. Marine areas are very susceptible to human influence, being located at the bottom of society. The reason that we know so little about them must not be interpreted as if they are more resistant to change. Pollution by mud, nutrients and chemicals causes very serious degradation. Currents transport problems far away, and as these cling to the land, pollution is exported to a large coastal area downstream, possibly in other countries.
• Do we have enough knowledge of the systems to manage them any better? Bad management is worse than no management at all. Management by belief, or based on assumptions, is bad management. We have the means to measure quantity and quality. By monitoring progress and basing management dicisions on observed facts, good management can make a positive difference. A farmer does not need to know about veterinary medicine to manage his cows. Good management can be based on observations and common sense.
• Do we have the confidence to allow systems to change if changes are not adverse? A silly question. If changes are not adverse, they must be good. Would we really like to disallow these? What do we want to achieve in the first place? Mention one human-induced change which has been good to nature.

M Elliott, A J Lawrence: The protection of species versus habitats - dilemmas for marine scientist. Marine Poll Bull 36/3 pp174-176, 1998

The basis of conservation biology is founded in four related scientific disciplines:

• ecology: the knowledge of ecosystems, communities and populations, and how these work.
• biology: the knowledge of individual species, their needs and life cycles.
• taxonomy: the identification and classification of species, necessary to identify species and to measure biodiversity.
• conservation: the practice and theory of conservation.

• vulnerability: of species, communities and populations. Although vulnerability (or resilience) is difficult to predict in advance, much can be learnt from similar situations which have happened already. (see also conservation value below)
• viable populations: populations must be able to maintain their numbers. Individuals must find breeding partners, and mating must result in offspring and stable numbers, without human intervention. The genetic variety of the population must be adequate to cope with adaptation. Since global changes are happening rather fast, populations must be able to adapt faster than they used to, and thus their genetic base must have ample variety. The size of a reserve is very important for this.
• inbreeding: small populations may lead to inbreeding, resulting in unsustainably poor genetic variability. These matters are particularly relevant for zoos and their role in species restoration (see reintroduction below).
• conservation value: politicians like to work with simple figures for conservation value. Nature's resilience is made up of several factors, of which three are most important, and they can be combined into a single conservation value: diversity (quality) x density (repetition) x functionality (connectedness). However, measuring these factors objectively is a problem.
• sizing nature reserves: the size of a nature reserve is critical to its success, relating to both the number of species saved, and their viability. However, the larger reserves are less likely to happen because such amounts of undisturbed habitat are rare and people pose limits to their generosity. (see also connecting corridors)
• reducing fragmentation: fragmentation reduces the effectiveness of a natural area considerably. Often due to ignorance, infrastructure is allowed to cross through contiguous natural areas, causing disproportionally large side effects. Roading, pipelines, canals, railways have all brought about serious fragmentation of contiguous habitat. Fragmentation can be reduced by allowing for passageways for wildlife, and by better planning.
• reducing boundary effects: wherever a habitat change is made, a boundary effect is created, making the change felt deep into the natural area, and upsetting the natural balance. Sometimes boundaries bring a succession of species (plant and animal) which enhances biodiversity, but at the expense of the original communities. The boundary effect can be reduced by reducing fragmentation, and by aiming for large, contiguous areas. Note in this respect that true islands, surrounded by water or sea (and oases surrounded by desert), have minimal boundary effects. Species from outside do not wander in, and species from inside do not wander out. When it comes to marine island reserves, the boundary effect is even positive - species from far afield seeking refuge, and the island acting as an oasis.
• connecting corridors: some conservationists believe that having many small reserves, equals that of a single large one, but they are mistaken in this, due to a large boundary effect, low viability and resilience. By interconnecting such reserves with corridors of similar habitat, species could be allowed to roam from reserve to reserve. However, the boundary effects of corridors is very large (outside predators intercepting the traffic), resulting in a continual drain of life from the interconnected reserves.
• shelter & refuges: in any habitat, shelters and refuges are very important against predation and adverse conditions. They are critical for niche species which are easily predated upon. For instance, nest boxes, although strictly unnatural, can make an enormous difference to the quantity and quality of populations.
• re-introduction: critically endangered species can be saved by ex-situ (out of place) breeding (see below), and then releasing into island enclaves where adverse effects such as predation have been eliminated. Successes have been recorded for species threatened by predation and habitat destruction.
• restoration of habitats: many conservationists believe that habitats can be restored. However, they may be wrong in this. A habitat is a complex web of communities on many trophic levels, which over time (1000 years), have changed their own environment, including soil and microclimate, to suit themselves. With the limited knowledge we have, it is impossible to achieve the same, and in a short time. Wherever habitats have been restored by replanting native plant species, the result has never been proved viable. From own observations, human-planted habitats end up as disasters in 10-30 years time, losing out to those areas which have been left to recover by themselves through natural successions of species. Conservationists are active in restoring wetlands with moderate success (they are the easiest ones, with simple soils and low canopies), and dunes with disastrous results (see  disappearing beaches/dune stabilisation).
• ex-situ conservation: some species are in such critical state that they need to be reared outside their environment in nurseries and zoos. This kind of conservation won't allow species to change in their roles within their natural habitats, and when put back into the environment, are bound to fail. It is also very costly and requires human intervention, perhaps forever. This kind of conservation has been practised for less than 30 years, and it is too early to say whether it will succeed in the long term. However, all attempts to release juvenile marine species back into the wild have failed so far.
• monitoring: monitoring the environment is an important but expensive and sometimes boring aspect of conservation biology. It is essential because it provides the feedback necessary to judge the results of actions. Just imagine having to somehow measure the numbers of individuals of some hundreds of species, along transects and inside plots (samples) in many places. No surprise then, that scientists are looking for shortcuts, such as indicator species (see below) and physical samples of water, air and soil.
• indicator species: ideally, an indicator species is an organism which is sensitive to one and only one threat (one kind of chemical or biocide or other stress), and which is not harvested by humans. The search is on for the holy grail of indicator species. However, success is unlikely because the idea is not in accordance with the way species have evolved naturally. If one species disappears, then a number of other species will also be affected. In the end, what do we learn from indicator species that would have changed our actions?

I have observed that the juveniles of most (marine) species are good indicators of stress. Established individuals appear to survive better than those who wish to establish themselves. The ratio of young to old individuals I have found to correspond quite well with the amount of degradation observed. Another good indicator is the number and quantity of species who do not belong in the habitat. They are usually the opportunistic, fast-growing species (like weeds), occupying vacant territory left behind by the death of others.

• artificial breeding: crop plants and livestock have for centuries been bred under closely supervised conditions. Improvements were made by (unnatural) selection, resulting in incredible advances in productivity. Fertilisers and biocides have been tested in similar ways, resulting in very finely detailed knowledge about crop management and animal husbandry. Artificial insemination has spread the genes of a few male animals far across the world. The world of today would have been unimaginable without this. However, the availability of more food has helped human populations to grow to the threat they pose today. The genetic basis of our important crops has become very narrow, rendering seeds unsuitable for propagation. Many commercial crops have been rendered infertile to protect intellectual property rights, preventing local farmers from using their seeds for the next harvest.
• freezing: genetic material such as sperm can be stored almost indefinitely, giving scientists access to a large source of genetic information. It can be transported easily and used to fertilise many receptors.
• seed banks: the seeds of cultivated and indigenous plant species have been collected worldwide, and stored in seed banks. It gives scientists access to a large base of genetic information. These seed banks also store the seeds of plant varieties no longer used for commercial production (old varieties of fruits, and so on). However, seed banks are no substitute for living species, and they may be risky due to the absence of replication. Plants stored in seeds can no longer adapt to a changing environment.
• genetic engineering: the techniques of genetic engineering (GE) have given scientists a formidable tool for improving crops. Remember that the path of evolution requires a viable parent before viable offspring can be produced. Improvement can be obtained only from the genes already present in the parents. Nature's way of trial and error has been erratic rather than purposeful, but given enough tries, it has come up with amazing results (and a lot of unused genetic garbage in each species' genome). By contrast, genetic engineering brings purpose in the evolutionary process, while speeding it up considerably. It can make offspring with genes not originating from its parents, but the offspring must still be viable. The promises of GE are almost unlimited, and here are some:
• productivity: further advances are expected in productivity, by using less water, less fertiliser, while producing less woody substances, growing faster and producing heavier fruits and seeds. Advantages are obvious.
• disease resitance: disease resistance from other plants can now be transferred to important crops, resulting in less use of biochemicals, which is of considerable benefit to the environment.
• herbicide resistance: resistance to certain chemical weed killers allows farmers to do away with ploughing and discing for weed control, resulting in considerable benefit to the quality of the soil.
• self-fertilising: successful crops have symbiontic bacteria in their roots, which produce nitrogen fertiliser from air. Such properties are transferable by GE, resulting in reduced use of fertilisers, and thus reduced nutrient runoff, and reduced costs, while also improving soil quality.
• shorter season: crops can be made to flower and to seed sooner, shortening the required season of warm, moist weather. It allows farmers to have more predictable harvests, and would make more regions suitable for cropping.
• salt resistance: plants do not need salt, but suffer from an excess of it. Repeated irrigation in dry lands, has resulted in the soil becoming too salty for ordinary crops. But GE can make crops more tolerant, such that abandoned lands may become productive again. However, in the end the salt continues to accumulate.
• local temperature: crops can be adapted to the temperatures of a given region, so that nations can become more selfsufficient, while also reducing transport costs.
• cloning: once an organism with all the desired characteristic has been produced, it can be cloned exactly as it is to produce an unlimited number of offspring, thereby eliminating the vagaries of sexual reproduction.
• integrated pest management (IPM): not yet a branch of GE, it nonetheless uses advances made in agritechnology. The idea of IPM is to attack pests by various means, all at the same time. Some of it is chemical, but most biological (infertile males, pheromone baits, parasitic wasps, outbreak monitoring, perfect timing, etc.).
• and so on.

(a separate chapter will be devoted to Genetic Engineering on this web site)
 
 
 

The boundary effect The size of a reserve is not only important for its biodiversity, sustainability and resilience. It is also important to minimise the boundary effect, caused by the transition from one environment into another.

This diagram illustrates some aspects of the boundary effect. The green area is the reserve, surrounded by alien habitat in white. The boundary effect is shown in light green. It is caused by native species moving out or being predated upon by exotic species living in the alien habitat, or near its boundary. At the same time, exotic species move into the reserve to take up nesting space and so on. Through competition, the characteristics of the boundary will be different from those within, the pristine core.
As can be seen, the smaller the area, the more of the reserve is occupied by boundary. Thus large reserves have relatively less boundary area (B). The worst shape is that of a strip or ribbon (C), yet many reserves, especially marine reserves following coastlines, are shaped this way. Note that because the boundary runs along the outside, along the largest diameter, it will always be a large area.
It is commonly thought that two adjacent reserves can be joined to become one big one, by means of a wildlife corridor. However, if such a corridor is a narrow strip, it will be dominated by the boundary effect, resulting in a possible drain to both reserves. Wildlife will stray into the corridor, where predators will wait for it.

A boundary effect, particularly relevant to marine reserves, is that of fish spilling over to the unprotected, outside area. Fishing will always occur at the boundaries of such reserves, because of it. The classical approach is that of creating a ribbon reserve around a highly diverse habitat such as a rocky shore (A). By placing the reserve boundary across the protected habitat, fish will spill out and get caught. The reason for this happening is that fish are continually competing for territories. Fish caught in the unprotected part of the rock habitat, leave empty territories behind. Fish from the protected habitat will move into these, because they do not know about reserve boundaries. Fish deeper into the reserve find adjacent territories unoccupied, and they move closer to the reserve's boundary, and so on. The result is an unexpectedly large drain from the protected area.
By contrast, if the boundary is placed across a different habitat (B), fish of the rocky habitat will be restrained naturally. They won't move into the sandy habitat, but they may forage there. As a result, the spilling over is reduced quite considerably. It follows that the placement of reserve boundaries is critical to a reserve's success, and should be chosen with care. Political compromises can do great harm.