Walking Wetlands

The idea of a wetland that can move from place to place is an odd one, but in many ways it is not a new one. Basically, a walking wetland is when someone floods a piece of land and lets a wetland grow there for a while. Then, after some pre-determined amount of time has passed, that piece of land is drained and a different piece of land is flooded. A wetland is then allowed to grown on the new piece and, viola, the wetland has walked!

This technique is a lot like crop rotation schemes that have been around for just about as long as agriculture. Letting land lay fallow lets that land recharge some of its nutrients and so be more fertile the next time a crop is grown on it. Walking wetlands are just another type of rotations, but this rotation is to cover the land with shallow water. Not much water is needed to make this work. Generally, about 4 inches is the average depth! Letting the land be flooded in those 4 inches for from 1 to 4 years lets amazing things happen!

First year walking wetland in the Klamath Basin.

For one, a lovely wetland springs up quite quickly. In the first year, the area is generally covered in grasses and other fairly short plants that only raise above the water a relatively short distance and that grow in a fairly open pattern with lots of space for shorebirds to walk around and forage. In the second year, tules and cattails grow up. This form tall and dense stands. The small open patches are preferred by a wide range of duck species though the shorebirds don’t tend to like this habitat as much. In subsequent years, some habitat modification, such as mowing, is generally needed to keep the tules and cattails at a level that still allows for birds and other wildlife species to access the wetland. Otherwise the stands of tules and cattails grow so dense that only a few species will utilize them.

Another amazing thing is that some crop pathogens that live in the soil drown. Many pathogenic microbes cannot survive a year or two of being submerged. Impressively, many beneficial soil microbes actually can survive this long underwater, so when the land is drained, the good microbes are still present and many of the bad ones are gone! This has an economic benefit because growers then need to buy less pesticides. This has an environmental benefit because grower need to apply less pesticides.

A third amazing thing is that all the birds that come and use the wetland leave their waste behind! Bird guano is fantastic fertilizer, and having a few thousand ducks, geese, and shorebirds wandering around can result in the grower needing to buy and apply less fertilizer and also lead to a boost in crop production!

An older walking wetland in the Klamath Basin.

Along the Pacific Flyway, walking wetlands have been really pioneered in the Klamath National Wildlife Refuge along the California-Oregon boarder, which is home to the first officially titled Walking Wetlands Program. It has since also been adopted in the Skagit Valley in northern Washington state. Additionally, several groups in central California, including the Sacramento-San Joaquin Delta Conservancy where I work, are looking at using walking wetlands in the California Delta.

For better or for worse, setting aside habitat exclusively for wildlife use is not going to be able to secure enough land to protect that majority of species. Instead, finding ways for agriculture and wildlife to both succeed is the only way that longer-term conservation is going to be successful, and walking wetlands are a terrific example of what that can look like.

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Principles of Reserve Design

It is generally acknowledges that one of the very best way to protect biodiversity is by setting aside areas of land in reserves and allowing natural processes to proceed largely uninterrupted. These reserves can be in a variety of forms including national parks, protected watershed, or on private property when the owner has agreed to set aside land for conservation easements.  But when the time comes to decide what land should be protected, how much, and in what arrangements, different variables need to be taken into account. Here are some guidelines that are often considered when setting aside land for conservation.

1. It is generally better protect a complete ecosystem. If a whole watershed can be protected, that would be better than if part of the watershed was outside the reserve.

2. Larger reserves are generally better than small one. Large reserves are more likely to have many habitat types and hold larger populations of the species in those habitats. this means that if the choice is to set a side a small area off by itself or add to an already existing reserve, the existing reserve should be expanded.

3. Having a reserve that is unfragmented is better than having one that is fragmented. The fewer roads, power lines, etc. that pass through a reserve the more continuous the habitat will be and so have fewer edge effects.

4. Having more reserves is better than having few reserves.

5. Connecting reserves with corridors is better than having reserves that are isolated from one another. Corridors will be different for different species, for example Black Bears seem to like to use tunnels to get under a road, but Grizzly Bears prefer bridges over the road.

6. In the absents of corridors that connect reserves, creation of stepping-stone reserves can have similar effects. Stepping-stone reserves are smaller reserves that lie between larger reserves. These serve to reduce the total dispersal distance that organisms have to travel to find suitable habitat.

7. Protecting an area with many diverse habitats is generally better than protecting areas that have fewer habitats.

8. A reserve that has a more uniform shape will have fewer edge effects and more undisturbed interior area as compared to a reserve that is long and thin or irregular in shape.

9. Generally speaking, having a variety of large and small reserves in an area is better than having reserves that are all the same size.

10. Managing the reserves in an area jointly is better than managing each one individually. This allows for more specialized and targeted management and better biodiversity protection region-wide.

11. Allowing humans to enter and utilize some of a reserve while protecting a core area is better than excluding humans altogether. While counter-intuitive, if humans are allowed to visit parts of a reserve they are much more likely to support the continued protection of that reserve from future development. If humans are excluded completely, they tend to not realize how important a reserve is.

Now, of course these guidelines are subject to the real world. If there is only one areas of land that has been put up for sale, and the choice is to protect it, or protect nothing, then it is probably better to protect that land even if it is small and isolated from other reserves. But, when choices are available, these guidelines help to create areas that most effectively protect biodiversity.

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Biodiversity And How It Is Measured

Biodiversity is the number of species in a given area. The largest measure of biodiversity is the estimated total number of species on the planet (somewhere around 10 million, although estimates of as high as 40 million are not unreasonable). Other scales are often more useful such as how many species occur in a country or mountain range or nature preserve. Ecologists have several measures for comparing diversity in different places.

Species Richness is the number of species found in a particular community. Measures of species richness such as the Shannon Diversity Index are weighted to show that one community if made of many species that all are equally numerous versus another community that has just as many species, but a small number are extremely numerous and the rest are quite rare. Species Richness can also be viewed at different special scales. Alpha Diversity is the number of species in a particular designated area suchas a park or reserve. For example, in the diagram below, Area 1 in Region 1 has an Alpha Diversity of 5. Region 1 has an average Alpha Diversity of 6 ((5+6+7)/3). Gamma Diversity is the number of species in a larger geographic area such as a mountain range or continent. For example, Region 1 has a Gamma Diversity of 7 (ABCDEFG). Beta Diversity is a measure of how species composition changes along an environmental or geographic al gradient such as moving from headwaters to mouth of a river. For example, Region 1 has a Beta Diversity of 1.2 indicating that most of the species that occur at one end of the gradient still occur at the other, in other words, there is low species turnover.

Region 1:     Area 1          Area 2          Area 3               Alpha     Gamma     Beta

Species:          BCDEF        ABCDEF      ABCDEFG              6                7            1.2

Region 2:     Area 1          Area 2          Area 3

Species:           ABC              DEFG            DGHIJ               4               10           2.5

Region 3:     Area 1          Area 2          Area 3

Species:           ABC               DEF                GHI               3                 9            3.0

As can be seen by comparing Region 1, Region 2 and Region 3 to each other, different arrangements of species can be represented with different measures of diversity. For example, while Region 2 has the highest total number of species (Gamma Diversity), Region 1 has the highest number of species per specific location (Alpha Diversity), and Region 3 has the highest turnover of species across the whole region (Beta Diversity).

There are other measures of diversity that are also useful in ecology. Genetic Diversity indicates how much variation exists at the DNA level in a species or population and is often used as a measure of how evolutionarily adaptable that species or population is. Ecological Diversity is a measure of how many different types of communities occur in a given ecosystem.

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Adding to a Jewel

Next year (2014) marks the 150th anniversary of the signing of the Yosemite Land Grant by President Abraham Lincoln.  And it looks like the “Crown Jewel of the National Park System” is going to grow with age.  A proposal was introduced to congress by Senator Dianne Feinstein and Representative Jim Costa, both from California.  It is currently working its way through the federal government, and will add 1,600 acres to the western edge of the park next year!  The tract of land is currently owned by a combination of  private individuals and a group called the Pacific Forest Trust, and it includes foothill habitats and overlooks central valley of California.  The private land will be purchased and the Pacific Forest Trust is donating the rest.

I think this is really wonderful event.  Admittedly, if you look at a map of Yosemite and see what 1,600 extra acres adds, you will probably not be impressed.  In comparison to the whole park, 1,600 acres is a tinny little addition, but it is exactly through small increases that large tracts of land can be protected.  And protecting large tracts of land is the best way to insure that biodiversity will be preserved in the future.  Especially in the face of climate change, we don’t really know how the ecosystems of the world are going to change.  Generally, species are likely to move towards the poles and up the sides of mountains, but the world will be rife with exceptions to those general trends.  Preserving lands in large enough pieces to allow for taxa to move around, or move into a new area, and still find suitable habitat is the smartest strategy for insuring that as many species as possible are able to persist.

Stemming from biogeography there has been an ongoing debate in conservation circles for about half a century about they best way to preserve land in order to protect biodiversity.  One side focuses on preserving large tracts of land even though there will be few of these tracts.  The other says that many small tracts will more effectively preserve overall biodiversity.  But, both sides agree that the best outcome of all is many large tracts.  So, we as a society should attempt to increase the size of any preserve any time we can.  If that means buying a small tract of land and creating a preserve where there was none before, that is terrific.  If it means adding to a small preserve and so making it somewhat larger, that is also terrific.  If it means adding to a preserve that is already very big, like Yosemite National Park, that is terrific as well and should not be trivialized.

So, after the addition is added to the park, go out and visit the new portion of Yosemite!

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