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As islands get larger, the number of species accelerates, although the effect of island area on species numbers is not a direct correlation. Conservation preserves can be seen as “islands” of habitat within “an ocean” of non-habitat. For a species to persist in a preserve, the preserve must be large enough. The critical size depends, in part, on the home range that is characteristic of the species. A preserve for wolves, which range hundreds of kilometers, must be much larger than a preserve for butterflies, which might range within ten kilometers during its lifetime. But larger preserves have more core area of optimal habitat for individual species, they have more niches to support more species, and they attract more species because they can be found and reached more easily.

Preserves perform better when there are buffer zones around them of suboptimal habitat. The buffer allows organisms to exit the boundaries of the preserve without immediate negative consequences from predation or lack of resources. One large preserve is better than the same area of several smaller preserves because there is more core habitat unaffected by edges. For this same reason, preserves in the shape of a square or circle will be better than a preserve with many thin “arms.” If preserves must be smaller, then providing wildlife corridors between them so that individuals and their genes can move between the preserves, for example along rivers and streams, will make the smaller preserves behave more like a large one. All of these factors are taken into consideration when planning the nature of a preserve before the land is set aside.

In addition to the physical, biological, and ecological specifications of a preserve, there are a variety of policy, legislative, and enforcement specifications related to uses of the preserve for functions other than protection of species. These can include anything from timber extraction, mineral extraction, regulated hunting, human habitation, and nondestructive human recreation. Many of these policy decisions are made based on political pressures rather than conservation considerations. In some cases, wildlife protection policies have been so strict that subsistence-living indigenous populations have been forced from ancestral lands that fell within a preserve. In other cases, even if a preserve is designed to protect wildlife, if the protections are not or cannot be enforced, the preserve status will have little meaning in the face of illegal poaching and timber extraction. This is a widespread problem with preserves in areas of the tropics.

Limitations on preserves

Some of the limitations on preserves as conservation tools are evident from the discussion of preserve design. Political and economic pressures typically make preserves smaller, never larger, so setting aside areas that are large enough is difficult. If the area set aside is sufficiently large, there may not be sufficient area to create a buffer around the preserve. In this case, an area on the outer edges of the preserve inevitably becomes a riskier suboptimal habitat for the species in the preserve. Enforcement of protections is also a significant issue in countries without the resources or political will to prevent poaching and illegal resource extraction.

Questions & Answers

what is photosynthesis
Victor Reply
The process plants use to convert sunlight into food (energy).
juanita
Some other organisms use
juanita
types of photosynthesis
Victor
ps1 and ps2
smritilekha
what is used to determine phylogeny?
Israel Reply
which condition is the basis for a species to be reproductively isolated from other members?
Israel Reply
Why do scientists consider vestigial structures evidence for evolution?
Israel
8.Which statement about analogies is correct?
Israel
What is true about organisms that are a part of the same clade?
Israel
Why is it so important for scientists to distinguish between homologous and analogous characteristics before building phylogenetic trees?
Israel
(CH2O)n is the stoichiometric formula of
Marcellus Reply
what are nucleotide
Anastijjaninaiya Reply
Methane,ammonia,water and sugar are dissolved to form nuceotide
Me
Introduction To Biology
Tanveer Reply
can ringworm be caused by bacterium
fred Reply
Nope
ejikeme
Branches of biology
Tanveer
no it does not occurs by bacterium
gopal
what is a brick?
Istifanus Reply
what is gene in biology?
yousaf Reply
it is a heredity unit
Me
what is DNA
yousaf Reply
carrier of genetic information
missy
deoxyribonucleic acid
gopal
it contains genetic information and brings it to one generation to other
gopal
it is of two Types circular DNA and linear DNA
gopal
plasmids are the type of small circular DNA which lies outside the genomic DNA
gopal
And what makes a virus to be difficult to destroy
Mosongo
what observation is made when dry seeds and soaked seeds are put in a vacuum flask
Robin Reply
there is respiration from the soak seeds which shows on the walls of the vacuum flask
Israel
what's mammals ?
Istifanus Reply
mammals are vertebrates ,any member group of vertebrates animals in which the young are nourished with milk from special mammary glands of the mother.
yousaf
what are actin and myosin
Praveen Reply
they are muscle filaments
Israel
they make up the microfibrils of the muscle ,relaxing and contracting to cause movement
Israel
Please did anybody know the questions that will come out in the coming practical?
Oladimeji
Why it is importantthat there are different types of protein in plasma membraine for the transport materials into and out of a cell?
Louellie Reply
the nerve cell
Mustapha Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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