Petitioners seek a writ of prohibition to prevent respondent Secretary of State Ralph Munro from processing or certifying proposed referendum measure 41 to election officials for submission to the voters at the general election on November 6, 1984. See Const. art. 4, § 4; RAP 16.2(a). The referendum was filed on March 22, 1984, by respondent intervenors Eleanor Fortson and The Committee to Maintain a Fair Timber Tax. The referendum is to the timber tax act (the Act), Laws of 1984, ch. 204, §§ 3-7, p. 1002. On May 23, 1984, this court, by order, granted the writ of prohibition ordering the Secretary of State to refrain from taking any action to process or certify proposed referendum measure 41 for the November 1984 election.
Prior to 1972, most growing timber and underlying commercial forest land in the state of Washington was assessed and taxed as other real property. By the enactment of Laws of 1971, 1st Ex. Sess., ch. 294, the Legislature introduced a different tax system for forest lands. While ad valorem property taxation was continued based on the value of the underlying forest land, an excise tax payable at the time timber is harvested was substituted for the former ad valo-rem tax on growing timber.
The Legislature did not, prior to 1984, fix a permanent excise tax rate for timber harvest. Instead, a temporary tax of limited duration was enacted and subsequently extended by the Legislature several times.
Laws of 1983, 2d Ex. Sess., ch. 3, § 59, p. 2195, codified at *763RCW 84.33.071, provided for a tax on the harvesters of timber as follows:
(1) Upon every person engaging within this state in business as a harvester of timber; as to such persons the amount of tax imposed with respect to such business shall be equal to the stumpage value of timber harvested between July 1, 1983, through June 30, 1984, for sale or for commercial or industrial use multiplied by the rate of six and one-half percent.
(Italics ours.)
In 1984, the Legislature passed Senate Bill 4421 which provided in part:
New Section. Sec. 2. (1) An excise tax is imposed on every person engaging in this state in business as a harvester of timber on privately or publicly owned land. The tax is equal to the stumpage value of timber harvested for sale or for commercial or industrial use multiplied by the rate provided in this chapter.
(2) A credit is allowed against the tax imposed under this section for any tax paid under section 8 of this act.
(3) Moneys received as payment for the tax imposed under this section and section 8 of this act shall be deposited in the timber tax distribution account hereby established in the state general fund.
New Section. Sec. 3. The rate of tax imposed under section 2 of this act for timber harvested July 1, 1984, through June 30, 1985, shall be six and one-half percent.
New Section. Sec. 4. The rate of tax imposed under section 2 of this act for timber harvested July 1, 1985, through June 30, 1986, shall be six and one-eighth percent.
New Section. Sec. 5. The rate of tax imposed under section 2 of this act for timber harvested July 1, 1986, through June 30, 1987, shall be five and three-fourths percent.
New Section. Sec. 6. The rate of tax imposed under section 2 of this act for timber harvested July 1, 1987, through June 30, 1988, shall be five and three-eighths percent.
New Section. Sec. 7. The rate of tax imposed under section 2 of this act for timber harvested July 1, 1988, and thereafter, shall be five percent.
*764Laws of 1984, ch. 204, §§ 2-7, p. 1002.
The proposed referendum states it is:
To be submitted to the people at the General Election of November 6, 1984.
Sec. 3. The rate of tax imposed under section 2 of this act for timber harvested July 1,T984, through June~30j 1985, shall be six and one-half percent.
Sec. 4. delete entire section.
Sec. 5. delete entire section.
Sec. 6. delete entire section.
Sec. 7. delete entire section.
Const. art. 2, § 1(b) (amend. 7) provides:
Referendum. The second power reserved by the people is the referendum, and it may be ordered on any act, bill, law, or any part thereof passed by the legislature, except such laws as may be necessary for the immediate preservation of the public peace, health or safety, support of the state government and its existing public institutions, either by petition signed by the required percentage of the legal voters, or by the legislature as other bills are enacted . . .
(Italics ours.) The seventh amendment contains two separate and distinct exceptions from the power of referendum: Laws as may be necessary for (1) immediate preservation of the public peace, health or safety, or (2) support of the state government and its existing public institutions. Farris v. Munro, 99 Wn.2d 326, 335-36, 662 P.2d 821 (1983).
Petitioners contend the Act is necessary for support of the state government and therefore exempt from the referendum process. Respondents urge an interpretation of the Act which would subject it to referendum. Although the Legislature provided a continuation of the timber tax, due to expire on June 30, 1984, at a rate of 6.5 percent from July 1, 1984 through June 30, 1985, Laws of 1984, ch. 204, § 3, p. 1002, respondents point out it also specified yearly incremental reductions in the tax rate, culminating in a permanent rate of 5 percent on timber harvested July 1, 1988 and thereafter. Laws of 1984, ch. 204, §§ 4-7, p. 1002. Because the latter provisions reduce the timber tax rate, respondents assert they cannot be necessary for the support *765of government, and thus sections 4 through 7 are subject to the referendum.
We are persuaded neither by respondents' attempt to isolate sections of the Act nor by their speculative argument that incremental reductions in the tax rate will reduce revenues. While "any part" of an "act, bill, or law" as passed by the Legislature is subject to referendum, if there are "laws as may be necessary for the . . . support of the state government and its existing public institutions", such laws are not subject to referendum. Const, art. 2, § 1(b) (amend. 7). We have already held that to determine whether an act of the Legislature is subject to referendum we must consider the act as a whole, not piecemeal. See State ex rel. Helm v. Kramer, 82 Wn.2d 307, 316-17, 510 P.2d 1110 (1973).
The various sections of the Act, 49 in total, comprise a comprehensive system of taxation on timber, with the clear purpose of raising revenue. These sections are "integral parts of the legislative plan", State ex rel. Pennock v. Coe, 42 Wn.2d 569, 585, 257 P.2d 190 (1953).
Without passage of the Act, taxes on the harvesters of timber would have ceased on June 30, 1984. RCW 84.33-.071. Laws of 1984, ch. 204 is necessary for support of the state government. Farris v. Munro, at 336-37; State ex rel. Hoppe v. Meyers, 58 Wn.2d 320, 327, 363 P.2d 121, 100 A.L.R.2d 304 (1961); State ex rel. Reiter v. Hinkle, 161 Wash. 652, 657-58, 297 P. 1071 (1931).
As a result of study and analysis of modernized systems of taxation of timber, the Legislature proposed and passed the Act "to assure the citizens of this state and its future generations the advantages to be derived from the continuous production of timber ..." Laws of 1984, ch. 204, § 16(1), p. 1007. We do not speculate whether the lowering of the tax rate from 6.5 percent to 5 percent between 1984 and 1988 would lessen or increase the support of state government. Such a venture on the part of this court is both inappropriate and irrelevant.
The 1984 timber tax act is immune from the referendum *766process under Const. art. 2, § 1(b) (amend. 7).
The writ of prohibition is granted.
Williams, C.J., and Brachtenbach, Dimmick, and Pearson, JJ., concur.