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Human Impacts As a coastal habitat, the intertidal zone endures a variety of negative human impacts. Some harm occurs as a direct result of our visit either through trampling or collecting. Other effects on the ecosystem occur indirectly, through urban runoff for example, as a result of being neighbors with a large human population.
TramplingThousands of people explore the rocky intertidal areas in San Diego each year and have a direct impact on the organisms underfoot. Animals living in tide pools overcome enormous environmental obstacles everyday with clever behaviors and impressive physical feats only to be crushed by generally well-intentioned but unaware humans. The greatest impact can often be seen and felt through the loss of algae as they are tread upon and worn away resulting in a loss of habitat. Even the most careful tide pool visitor may be surprised to discover the number and variety of organisms that we unavoidably step on during our explorations. Specific advice for the intertidal zone at Bird Rock can help keep animals alive and knowing why it's important to lessen our impact can make it easier to do. Follow these links to learn more: CollectingThough it can be tempting to take a crab or snail home as a pet, the chances those animals will survive are very small. Bird Rock is subject to the regulations of the Department of Fish and Game with regard to collecting mollusks and other invertebrates for consumption or otherwise. Their guidelines can be found here. PollutionUrban runoff is pollution that is washed by rain, sprinklers and any running water from our yards, streets and other urban spaces into nearby waterways and eventually into the ocean. Here in San Diego, eventually doesn’t take very long at all. Often, when the runoff gets to the ocean it goes right through the intertidal zone at its highest concentration before it disperses offshore.
  A storm drain in the cliffs above Bird Rock The view looking down from the storm drain The pollution that gets washed away includes pesticides, herbicides and fertilizer from our lawns, car fluids from roads and driveways, pet waste, and general litter. The quantity of pollutants that lie waiting to be swept into the ocean can vary tremendously depending on our behavior. When beaches are closed after a rainstorm to protect humans from toxins in the runoff, the tide pools have to stay open for their inhabitants. Decreasing our toxic contribution to urban runoff is an opportunity for every individual to make a small difference. And it is the little things added up that will make a significant difference in the end. Plus, if you involve a neighbor, you’ve doubled your (positive) impact! What We Can Do Though we inevitably cause some impact to organisms or their habitats
when we visit Bird Rock, by no means should we forfeit our exploration.
Rather, we should tread lightly and with enlightened intent as we
pursue our interest in our immediate ocean neighbors. Vulnerable tide pool critters can use our help.
 Sea anemones at Bird Rock tend to live on the algal turf within ten or so yards of the boulders on shore. When the tide recedes and the anemones are exposed, they pull in their tentacles and close up into a small mass of jelly. To protect against drying out, anemones have small pieces of rock and shell stuck to their outer layer so once they have closed up, they are very difficult to see and therefore quite easy to step on. Click here to see a wider view of sea anemones blending in with the turf.
 Hermit crabs face two problems: first, they are easy to catch and pick up, which can be a fun experience for tide pool explorers; and second, they occur in high concentrations in some areas of Bird Rock. Holding a hermit crab in a wet hand and gently putting it back in its home pool should pose no real threat to this entertaining animal. However, being dropped from a height, relocated to a different pool or put in a bucket and taken home can cause varying levels of disruption or harm to a hermit crab. When found in high concentrations, as happens close to the actual Bird Rock where many football-sized rocks make up the terrain, hermit crabs can be hard to avoid underfoot and the telltale crunch will be your first indication you might try to find a new route.
Snails, limpets, mussels and barnacles that live on exposed rocks face the basic threat of being crushed if we step from boulder to boulder without looking or we walk on Bird Rock without noticing the animals dispersed across its surface. Keep an eye on where your feet are headed before they get there and you are likely to save one of these lives:
Just when we think we are safe from causing harm as we walk across the flat slabs of rock covered with the algal turf, it turns out that in a small patch of turf – a few square inches – live hundreds of small animals. Some of these animals are smaller than ants and others are the size of a dime. From the perspective of these organisms, their algal habitat is very much like a forest and home to hundreds of animal species.
Once we are aware of the impacts we can have on a place, it is important to make our experience there worthy. So step lightly, handle gently, and appreciate everything you can learn from this fascinating ecosystem! Why We Should Care
So what does it matter if a few tide pool animals die? Though the value of an organism – or even a species – to humans can be hard to determine, the value of that organism or species to its community can be quite high, and even critical to the survival of the ecosystem. Value to the Ecosystem: Biodiversity
How many species would have to be killed off at Bird Rock before that ecosystem collapses? Do we really want to find out? In an area of Bird Rock seen below, the bare tops of the low-lying rocks (extending diagonally from the lower right corner) normally covered by high tide indicate areas that have experienced heavy human traffic. The algal turf has been eroded away removing the algae and the habitat they provide other organisms.
As a casual or first-time visitor to any ecosystem, how do we know if biodiversity is high or if it is low? How can we judge which organisms are more valuable to the ecosystem and therefore should be carefully protected? Because we often can’t know the answers to these questions, it’s a good idea to do as little damage as possible.
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Brittle stars and shore crabs will both give up a leg to attempt an escape after being caught by a predator. Though this loss of limb won’t necessarily kill the animals directly, it can make them less fit for survival until the leg has grown back. If an up-close look is desired, try shooing the animal into a clean container with water in it for a short period of time and then be sure to set it free close to where you found it.
They do get some structural protection from the algae and it is likely that many of
them survive our average footsteps, but a jump down from a boulder or the grind
of a pivoting toe is probably more damaging than we could imagine. Get a closer look at the ‘invisible’ population of Bird Rock in the algal turf photo gallery found on the Life at Bird Rock page. 
How many hermit crabs would have to be crushed before they disappeared from Bird Rock for good? What about mussels? What about sea stars? The unmeasured answers to those questions are quite a few, not so many, and they are hardly there now. Each organism fills a role in its immediate habitat; the byproduct of its attempts at survival benefits other members of the ecosystem. Some are producers (algae) and provide a base food source as well as protection from the sun and predators. Some are detritivores or scavengers and consume organic waste converting minerals and nutrients into a useable form for other organisms. Some are herbivores and help clear space on rocks for others to settle and live. Some are carnivores and help other organisms from overpopulating and destroying the habitat. In a strong ecosystem with high biodiversity, members of different species overlap in each niche so if one organism and its adaptations aren’t sufficient for survival under given conditions, an alternately equipped organism may have better luck and the secondary service to the ecosystem is maintained.