a project I worked on over the last several months.
I am not a wetlands expert. But I definitely learned a lot about wetlands while working on this project.
My supervisor asked me to look into wetland conversions based on some things she was seeing in our field offices.
We wanted to quantify the extent and location of wetland conversions in NJ.
There was concern that the findings from this study --- locations of potentially illegal wetland conversions --- would be controversial.
But the focus of this project was to understand where (and when) conversions were occurring with the goal of educating our field staff to help prevent illegal conversions in the future.
(It us up to folks above me, to decide what to do with the information presented here.)
Here is my outline. ~30 slides total
Wetlands – soils, veg, hydro Converted – has been drained Ag wetland – former wetland area that is now used for agriculture
This slide also includes some facts about wetlands losses in the US going back to 1984.
The mid-1980s were important years in terms of wetland protections.
WC Provisions were passed in 1985.
The last statement on this slide emphasizes the importance of the WC provisions.
For those who don’t know where it is, I have this slide. NJ is the 4th smallest state in the US . (RI, DE, CT are smaller)
NJ is the most densely populated state in the country. But we are very proud to be the Garden State. As far as agriculture, NJ ranks 8th in the nation for nursery and horticultural sales. Vegetable farming and the horse industry are also big in NJ.
In NJ, we actually have several statewide Land Use/Land Cover datasets.
NJ uses a Modified Anderson LC Classification System.
These are the Level 1 Categories.
For this project, we were interested in all land that was in the “2140 Ag Wetlands” category (also referred to as “ModAg,”) in 2012.
In looking at the land cover datasets, I found myself asking some more general questions about NJ’s land cover datasets…
First, I looked at all Level 1 land cover categories.
Looking at the numbers in the table: Urban-increase expected Ag-decrease expected Forest-decrease expected Water-big increase-unexpected!? --- explained by the next slide Wetlands-decrease-expected Barren-decrease
Grand total-increase unexpected!
This slide explains why there was a huge increase in water (and total acreage) in the state.
…shows the importance of understanding the data and any changes that may have occurred in the mapping methodology over the years.
Getting back to the question we were after…
The next few slides show other ways of looking at the results.
12 types in all.
Overall, the percentages are very low.
What do these conversions look like?
(Here is where I learned the most about our datasets and the conversions that had actually occurred.)
Here is an example showing the 1986 land cover data
It is labeled as a few different land cover types. But look at the skinny red polygons---labeled as cranberry bog, a type of ag wetland. But the interior is labeled as coniferous scrub/shrub wetlands.
The fact that these red polygons were classified as cranberry bog in ‘86 makes me think the interior area was a cranberry bog in 1986 as well. This makes me wonder about quality control on the 1986 dataset. (This was the first time NJ had created a statewide lc dataset.)
In the 1995 imagery, all this land is clearly Mod Ag.
We know this area was converted to Mod Ag at some point.
But without the 1986 imagery, there is no way to know if the conversion occurred before 1986 or not.
There were lots of examples like this. I’m not going to show you any more of those, because the goal was to find areas where we can definitely confirm that a wetland was converted since 1986.
After telling our Assistant State Conservationist for Programs about these results, she asked this question.
Because some conversions may have occurred before 1986, the 9,000 acre number here may be an overestimate.
But it does seem to indicate lack of attention to wetland conversions.
It will be up to folks above me to decide how to respond to the conversions identified here.
July 29-230-Trish Long
Using a Land-use
Change Analysis to
in New Jersey
Trish Long / July 2019
Wetland conversions in New Jersey
• How many acres of wetlands in NJ were converted to
agricultural uses since 1985?
• Where are these conversions occurring?
IV. Conclusions and Next Steps
Wetlands - defined by hydric soils, vegetation, and hydrology
– perceived as "wasted space" and were converted to other uses
– “By 1984, over half (54%) of all the wetlands in the United States were drained or filled
for development or agriculture.“
Converted wetlands – wetlands that have been drained, dredged, filled or
leveled or where woody vegetation has been removed
Agricultural wetlands - cultivated lands that are modified former wetland
areas, and which still exhibit evidence of soil saturation
Increased awareness of the environmental benefits
associated with wetlands prompted Congress to enact the
Wetland Conservation Compliance Provisions of the Farm
Bill in 1985.
– Farmers who drain, clear trees, fill, or otherwise manipulate wetlands so
that they can be cropped, may lose eligibility for USDA programs.
– Before doing any alteration to a wet area, including clearing trees or
maintenance of existing drainage, farmers should contact NRCS for a
The Wetland Compliance provisions are the only laws that
afford protection to many wetland types.
~7,700 square miles or ~5,000,000 acres
• The most densely
populated state in the
• The Garden State
• Ranks 8th for nursery
and horticultural sales
• Vegetable farming
Original question: What is the extent and location of wetlands
conversions to agricultural uses since 1985?
New Jersey’s Land Use/Land Cover datasets
• 1986 Land Use/Land Cover
• 1995/97 update
• 2002 update
• 2007 update
• 2012 update
• 2015 update
Original question, revised, due to available datasets:
“…between 1986 and 2012”
Note: The wetlands described here were photo-interpreted. They are
not on-the-ground delineations.
NJ’s Land Use/Land Cover Data –
Modified Anderson Classification System
2140 Agricultural wetlands (modified)
Land Use Change in NJ 1986 - 2012
New Jersey ~5,000,000 acres
Units = acres
1986 2012 Change
1000Urban 1,252,138 1,573,836 321,698
2000Agriculture 818,592 618,246 (200,347)
4000Forest 1,614,891 1,527,740 (87,152)
5000Water 248,052 1,067,097 819,045
6000Wetlands 940,442 900,380 (40,062)
7000Barren 71,646 55,341 (16,305)
8000Managed Wetlands 7,988 n/a
Grand Total 4,955,736 5,744,652 796,879
2) Summary by Field Office
acres of wetlands
converted to ag
wetlands by 2012
total acres of
wetlands in 1986
% of wetlands
Hackettstown (7 counties) 1,660.51 119,904.48 1.4%
Frenchtown (3 counties) 1,001.31 52,459.99 1.9%
Freehold (3 counties) 1,825.65 122,809.79 1.5%
Columbus (3 counties) 2,781.14 257,896.30 1.1%
Woodstown (2 counties) 1,029.24 88,756.00 1.2%
Vineland (3 counties) 1,194.75 253,893.74 0.5%
Total 9,492.58 895,720.30 1.1%
3) Visual Examples
New Jersey Aerial Imagery Datasets / Orthophotography
• 2012 imagery
• corresponds to the 2012 Land Use/Land Cover layer
• 1986 imagery
• not available
• 1995 imagery
• earliest, readily available and usable aerial photography available statewide
• Without 1986 imagery, we cannot verify the original
land cover classification.
• This study can only be used to verify conversions that
happened since 1995.
• The following slides show examples of verified
conversions since 1995.
Example 1. Camden County
Example 2. Burlington County
Example 3. Cumberland County
Example 4. Ocean County
Example 5. Burlington County
Of the 9,492 acres of wetlands that were converted to ag
between 1986 and 2012, how many acres were on lands
that NRCS has worked on?
Use GIS to overlay final results with Common Land Unit
Result: 81% (7,668 acres)
~9,000 acres of wetland conversions to ag uses may have occurred
in NJ since 1986.
This may be an overestimate.
Present this information to field office staff to raise awareness
of the issue.
Consider using imagery from 1980s to verify original land use
classification and accuracy of results presented here.
USDA-NHAP scans from the 1980s
Not georeferenced, not statewide, not readily available
But we are in the process of having the 1980s imagery processed
so that we can use it in the future.
USDA-Natural Resources Conservation Service
220 Davidson Ave
Somerset, NJ 08873